2014-23686. Endangered and Threatened Wildlife and Plants; Endangered Species Status for Trichomanes punctatum ssp. floridanum (Florida Bristle Fern)

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service, propose to list Trichomanes punctatum ssp. floridanum (Florida bristle fern), a plant subspecies from Miami-Dade and Sumter Counties in Florida, as an endangered species under the Endangered Species Act of 1973, as amended (Act). If we finalize this rule as proposed, it would extend the Act's protections to this plant and add this plant to the Federal List of Endangered and Threatened Plants.

DATES:

We will accept comments received or postmarked on or before December 8, 2014. Comments submitted electronically using the Federal eRulemaking Portal (see ADDRESSES below) must be received by 11:59 p.m. Eastern Time on the closing date. We must receive requests for public hearings, in writing, at the address shown in FOR FURTHER INFORMATION CONTACT by November 24, 2014.

ADDRESSES:

You may submit comments by one of the following methods:

(1) Electronically: Go to the Federal eRulemaking Portal: http://www.regulations.gov. In the Search box, enter FWS-R4-ES-2014-0044, which is the docket number for this rulemaking. Then, in the Search panel on the left side of the screen, under the Document Type heading, click on the Proposed Rules link to locate this document. You may submit a comment by clicking on “Comment Now!”

(2) By hard copy: Submit by U.S. mail to: Public Comments Processing, Attn: FWS-R4-ES-2014-0044; Division of Policy and Directives Management; U.S. Fish and Wildlife Service, MS: BPHC, 5275 Leesburg Pike, Falls Church, VA 22041-3803.

We request that you send comments only by the methods described above. We will post all comments on http://www.regulations.gov. This generally means that we will post any personal information you provide us (see Information Requested, below, for more information).

FOR FURTHER INFORMATION CONTACT:

Craig Aubrey, Field Supervisor, U.S. Fish and Wildlife Service, South Florida Ecological Services Office, 1339 20th Street, Vero Beach, FL 32960; by telephone [phone]; or by facsimile 772-562-4288. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why we need to publish a rule. Under the Endangered Species Act (Act), if we find that a species warrants listing as an endangered or threatened species throughout all or a significant portion of its range, we are required to promptly publish a proposal in the Federal Register and make a determination on our proposal within 1 year. Listing a species as an endangered or threatened species can only be completed by issuing a rule. In the near future, we intend to propose to designate critical habitat for Trichomanes punctatum ssp. floridanum under the Act. Critical habitat is prudent, but not determinable at this time. We will publish a proposal to designate critical habitat for Trichomanes punctatum ssp. floridanum under the Act in the near future.

This rule proposes to list Trichomanes punctatum ssp. floridanum (Florida bristle fern) as an endangered species.

The basis for our action. Under the Act, we may determine that a species is an endangered or threatened species based on any of five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. We have determined that the threats to Trichomanes punctatum ssp. floridanum consist primarily of destruction and modification of habitat resulting in changes in canopy, humidity, hydrology, and fragmentation (Factor A); and proliferation of nonnative invasive species, natural stochastic events including hurricanes and tropical storms, and impacts from climate change including temperature shifts and sea level rise (Factor E).

We will seek peer review. We will seek comments from independent specialists to ensure that our determination is based on scientifically sound data, assumptions, and analyses. We will invite these peer reviewers to comment on our listing proposal. Because we will consider all comments and information we receive during the comment period, our final determination may differ from this proposal.

Information Requested

Public Comments

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned governmental agencies, Native American tribes, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:

(1) Trichomanes punctatum ssp. floridanum' s biology, range, and population trends, including:

(a) Biological or ecological requirements of the plant, including habitat requirements;

(b) Genetics and taxonomy;

(c) Historical and current range, including distribution patterns;

(d) Historical and current population levels, and current and projected trends; and

(e) Past and ongoing conservation measures for the plant, its habitat, or both.

(2) Factors that may affect the continued existence of the plant, which may include habitat modification or destruction, overutilization, disease, predation, the inadequacy of existing regulatory mechanisms, or other natural or manmade factors.

(3) Biological, commercial trade, or other relevant data concerning any threats (or lack thereof) to this plant and existing regulations that may be addressing those threats.

(4) Additional information concerning the historical and current status, range, distribution, and population size of this plant, including the locations of any additional populations of the plant.

Please include sufficient information with your submission (such as scientific journal articles or other publications) to allow us to verify any scientific or commercial information you include.

Please note that submissions merely stating support for or opposition to the action under consideration without providing supporting information, although noted, will not be considered in making a determination, as section 4(b)(1)(A) of the Act (16 U.S.C. 1531 et seq.) directs that determinations as to whether any species is an endangered or threatened species must be made “solely on the basis of the best scientific and commercial data available.”

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the ADDRESSES section. We request that you send comments only by the methods described in the ADDRESSES section.

If you submit information via http://www.regulations.gov,, your entire submission—including any personal identifying information—will be posted on the Web site. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on http://www.regulations.gov.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on http://www.regulations.gov,, or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, South Florida Ecological Services Office (see FOR FURTHER INFORMATION CONTACT).

Public Hearing

Section 4(b)(5) of the Act provides for one or more public hearings on this proposal, if requested. Requests must be received within 45 days after the date of publication of this proposed rule in the Federal Register. Such requests must be sent to the address shown in the FOR FURTHER INFORMATION CONTACT section. We will schedule public hearings on this proposal, if any are requested, and announce the dates, times, and places of those hearings, as well as how to obtain reasonable accommodations, in the Federal Register and local newspapers at least 15 days before the hearing.

Peer Review

In accordance with our joint policy on peer review published in the Federal Register on July 1, 1994 (59 FR 34270), during the public comment period we will seek the expert opinions of appropriate and independent specialists regarding this proposed rule. The purpose of peer review is to ensure that our proposed listing determination is based on scientifically sound data, assumptions, and analyses. The peer reviewers will have expertise in Trichomanes punctatum ssp. floridanum' s biology, habitat, and physical or biological factors.

Previous Federal Actions

Trichomanes punctatum ssp. floridanum was first recognized as a candidate for possible future listing on November 9, 2009 (74 FR 57804), and we assigned the subspecies a listing priority number (LPN) of 3. Candidate species are assigned LPNs based on immediacy and magnitude of threats, as well as taxonomic status. The lower the LPN, the higher priority that species is for us to determine appropriate action using our available resources (September 21, 1983; 48 FR 43098). An LPN of 3 is the lowest LPN appropriate for a subspecies such as this fern, indicating that it is a high priority for the U.S. Fish and Wildlife Service (Service) to determine appropriate action. T. p. ssp. floridanum has remained on the candidate list with an LPN of 3 since 2009 (see 78 FR 70104, November 22, 2013; 77 FR 69994, November 21, 2012; 76 FR 66370, October 26, 2011; 75 FR 69222, November 10, 2010; 74 FR 57804, November 9, 2009).

On May 10, 2011, the Service announced a workplan to restore biological priorities and certainty to the listing process. As part of an agreement with the Center for Biological Diversity and WildEarth Guardians, we filed the workplan with the U.S. District Court for the District of Columbia. The workplan will enable the agency, over a period of 6 years, to systematically review and address the needs of more than 250 species, including Trichomanes punctatum ssp. floridanum, that were identified in our November 10, 2010, candidate notice of review (CNOR), published in the Federal Register at 75 FR 69222, ssp. floridanum to determine if these species should be added to the Federal Lists of Endangered and Threatened Wildlife and Plants. This workplan will enable the Service to again prioritize its workload based on the needs of candidate species, while also providing State wildlife agencies, stakeholders, and other partners clarity and certainty about when listing determinations will be made. On July 12, 2011, the Service reached an agreement with another plaintiff group and further strengthened the workplan, which will allow the agency to focus its resources on the species most in need of protection under the Act. These agreements were approved by the court on September 9, 2011. We are making this proposed listing determination for Trichomanes punctatum ssp. floridanum now as part of the court-approved workplan.

Background

It is our intent to discuss below only those topics directly relevant to the listing of Trichomanes punctatum ssp. floridanum as an endangered species in this proposed rule.

Species Description

Trichomanes punctatum ssp. floridanum, commonly referred to as the Florida bristle fern, is mat-forming, has no roots, and contains trichomes (hairlike/bristlelike outgrowths) on the tip of the fern (Wunderlin and Hansen 2000, pp. 153-154). This subspecies is very small in size and superficially resembles other bryophytes, such as mosses and liverworts, making it difficult to observe in its natural habitat. T. p. ssp. floridanum has thin veinlets (small veins) that are not enlarged towards the margin while veins are uniform in width to their apices (tips) (Nauman 1986, p. 179); fronds (leaves of ferns) are considered simple (Morton 1963, p. 89).

Wunderlin and Hansen (2000, pp. 153-154) described Trichomanes punctatum ssp. floridanum as having separated leaves, with the petiole (stalk by which a leaf is attached to a plant) 0.1-2.0 centimeters (cm) (0.04-0.79 inches (in)) long and typically shorter than the blade. The blade is fan-shaped, round, entire or irregularly lobed at the apex, and 0.5-2.0 cm (0.20-0.79 in) long and 0.2-1.1 cm (0.08-0.43 in) wide. This subspecies has few false veins, and its true veins are not enlarged at their apex.

One unique characteristic of this plant is that it lacks cuticles (the protective layer that cover the epidermis, which is the outermost layer of cells that cover the leaves) or has highly reduced cuticles, and has differentiated epidermises and stomata (small openings in leaves and stems through which gases are exchanged), causing dependence on elevated moisture conditions because a barrier is not present to prevent unregulated loss of water (Krömer and Kessler 2006, p. 57). This dependence restricts most Trichomanes spp. to shaded areas with high humid forested environments, making them more vulnerable to changes in localized climatic conditions (Schuster 1971, p. 91; Nauman 1986, pp. 181-182; van der Heiden 2014, p. 5).

Taxonomy

The genus Trichomanes contains approximately 320 species of ferns that occur primarily in the tropics and generally lack ecological information (Nauman 1986, p. 179; Nelson 2000, p. 77). The genus belongs to the family Hymenophyllaceae and the hymenophylloid clade, where ferns are also referred to as filmy ferns, which represents the thin, filmy leaves of the species (Nelson 2000, p. 77). The common name, bristle fern, is used to reference the bristlelike structure that protrudes from the mature sporangia (a structure that holds and produces spores) (Nelson 2000, p. 77).

Five species commonly known as bristle ferns (Trichomanes spp.) have been found in Florida (Krömer and Kessler 2006, p. 57). Trichomanes punctatum ssp. floridanum is a subspecies of Trichomanes punctatum, the current taxonomy of which is the result of monographic revision of Trichomanes sections (a taxonomic rank or position below the genus but above the species) Didymoglossum and Microgonium by Wessels Boer (1962, pp. 300-301). All U.S. species of Trichomanes now belong to the section Didymoglossum, except T. boschianum (Morton 1963). Wessels Boer, in reviewing specimens from throughout the American tropics, determined that all Trichomanes plants in Florida represented the same taxon, not two separate species, and that T. sphenoides (which he described as T. punctatum sphenoides) only occurred in tropical America and not in Florida. He further determined that Trichomanes plants in Florida were different from those in the tropics and described them as a new subspecies, Trichomanes punctatum ssp. floridanum (Boer 1962, pp. 300-301). This treatment has been followed by almost all subsequent authors (Lakela and Long 1976, p. 53; Wunderlin 1982, p. 32; Lellinger 1985, p. 205; Nauman 1986, p. 181; Flora of North America Editorial Committee 1993, p. 196; Wunderlin 1998, p. 44; Nelson 2000, p. 81; Wunderlin and Hansen 2000, p. 153; Wunderlin and Hansen 2003, p. 44). The only exception is Long and Lakela (1971, p. 73), who treated the subspecies as T. punctatum without further explanation. Additionally, the Florida Department of Agriculture and Consumer Services (2013, https://www.flrules.org/​gateway/​RuleNo.asp?​title=​PRESERVATION%20OF%20NATIVE%20FLORA%20OF%20FLORIDA&​ID=​5B-40.0055), the Integrated Taxonomic Information System (2011, p. 1), NatureServe (2013, http://explorer.natureserve.org/​servlet/​NatureServe?​loadTemplate=​tabular_​report.wmt&​paging=​home&​save=​all&​sourceTemplate=​reviewMiddle.wmt), the online Atlas of Florida Vascular Plants (Wunderlin and Hansen 2008, (http://www.florida.plantatlas.usf.edu/​Plant.aspx?​id=​1122), the Flora of North America (http://www.efloras.org/​florataxon.aspx?​flora_​id=​1&​taxon_​id=​233501316), and the Florida Natural Areas Inventory (FNAI, 2013, http://fnai.org/​trackinglist.cfm) use the name T. p. ssp. floridanum and indicate that this subspecies' taxonomic standing is accepted. In summary, there is consensus that Trichomanes punctatum ssp. floridanum is a distinct taxon.

Currently there are two extant metapopulations (a group of spatially separated populations) of this subspecies (Gann et al. 2002, pp. 552-554), comprised of four populations in Miami-Dade County and two in Sumter County separated by a distance of approximately 400 kilometers (km) (249 miles (mi)). Both extant metapopulations residing in Miami-Dade and Sumter Counties are considered T. p. ssp. floridanum; however, until recently, genetics sampling had not been conducted providing conclusive evidence that these metapopulations are in fact the same taxon. As noted by Small (1938, p. 50), the Sumter metapopulation is a considerable distance from where T. p. ssp. floridanum was first discovered (i.e., south Florida) and resides in a climate and habitat unlike the Miami-Dade County metapopulation. These differences are likely why Morton (1963, p. 90) suggested that the previous determination of these two metapopulations be reviewed. In March 2014, the Service contracted researchers from Florida Atlantic University to determine if the two metapopulations were the same subspecies. Samples were collected from both metapopulations for genetic analysis. DNA was isolated from the samples, and sequencing was completed on five samples from each metapopulation. Researchers found no observable differences in the sequence between the five samples collected from Miami-Dade County and the five samples from Sumter County, indicating that both metapopulations are the same subspecies (Hughes 2014, pp. 1-4).

Life History

The life cycle of ferns is not well known (Woodmansee 2013, pers. comm.); the specific life history of Trichomanes punctatum ssp. floridanum, including information on other members of the genus, is also lacking. Like all ferns, this taxon has two life-history stages, a gametophyte stage and a sporophyte stage. However, only the sporophyte form is recognizable in the wild, as spores of this plant are invisible to the naked eye (Possley 2013a, pers. comm.; van der Heiden 2013b, pers. comm.).

All reported populations of Trichomanes punctatum ssp. floridanum have been in the sporophyte stage. The initial stage, after a spore germinates, is the gametophyte stage. The gametophyte contains separate sperm and egg-producing structures. In the presence of water or moisture, sperm reach the eggs for fertilization. Fertilized eggs, under the proper conditions, develop into sporophytes—the typical form most ferns are observed in. The sporophytes produce spores, which in turn can germinate to produce new gametophytes (Nelson 2000, pp. 17-19). Reproduction may also occur in two other ways. Plants may reproduce by division, when rhizomes (horizontal, underground plant stems capable of producing the shoot and root systems of a new plant) break, forming clones of the parent plant, or they may also reproduce with the production of gemmae (cells that detach from the parent and develop into a new individual) and propagules (a plant part that becomes detached from the rest of the plant and grows into a new plant) produced by gametophytes, which can grow into new gametophytes of the same genotype (the genetic makeup of a cell or individual) (Dassler and Farrar 2001, p. 354; Hill 2003, p. 12).

Although it has been suggested that plants sporulate (produce spores) mostly in the spring and summer (Nauman, 1986, p. 182), field observations in Miami-Dade County have observed sporangia in the months of February, March, May, August, October, and December. The plants are likely fertile any time of year; however, during the dry season, sporophytes have been observed to desiccate and probably do not produce spores (Possley 2013e, pers. comm.). In Sumter County, sporangia have been observed from April through September; however, researchers suggest they are likely producing all year with peaks in the wet season (van der Heiden 2013c, pers. comm.). For Trichomanes punctatum ssp. floridanum, specific reproductive and growth requirements, such as moisture levels needed for each stage of its life history, plant longevity, growth rates, recruitment rates, dispersal methods, and genetic variation, are currently unknown.

Recent field studies in Sumter County on extant Trichomanes punctatum ssp. floridanum populations found average relative humidity to be around 95 percent, while ambient temperatures were recorded to stay around 23 degrees Celsius (°C) (73 degrees Fahrenheit (°F)). However, during cooler periods (19-22 °C; 66-70 °F) when humidity levels dropped slightly (to around 92 percent humidity), observed plant health declined, demonstrating the fragile nature of this taxon and its dependence on high humid conditions (van der Heiden and Johnson 2014, p. 9). This type of information needs to be further explored to determine habitat requirements (i.e., thresholds for humidity and temperature) for both metapopulations of this taxon.

Organizations such as the Institute for Regional Conservation (IRC) and Fairchild's Center for Tropical Plant Conservation (Fairchild) are working together to understand the biology, life history, and reproduction of Trichomanes punctatum ssp. floridanum. In 2002, IRC and Fairchild collaborated with fern culture experts from Marie Selby Botanical Gardens (MSBG) in Sarasota, Florida, and tissue culture experts at the Lindner Center for Conservation and Research on Endangered Wildlife (CREW) in Cincinnati, Ohio (Gann et al. 2009, pp. 35-36). Currently, Fairchild has grown 14 separate clusters from plants obtained in local hammocks (temperate hardwood forests) and monitored by their organization. The success of this effort to grow healthy T. p. ssp. floridanum has yet to be determined due to several factors including: slow growth rates, the formation of unusual linear fronds, the susceptibility to mold, and the lack of sporulation (Possley et al. 2013, pp. 43-45). However, researchers at CREW have recently developed a successful method to culture T. p. ssp. floridanum in-vitro and cryopreserve (to preserve by freezing at low temperatures) sporophytes (V. Pence, submitted; Pence and Charls 2006, pp. 29-34). The new plants from CREW have recently been transferred to MSBG, and plans are underway to establish T. p. ssp. floridanum onto limestone rock, which could potentially be transferred to solution hole (see description under “Habitat” section, below) walls for eventual reintroduction (Holst 2014, pers. comm.).

Habitat

In southeastern North America, Trichomanes spp. are considered rare because of their delicate nature and requirements for deeply sheltered habitats with almost continuous high moisture and humidity (Farrar 1993b, pp. 190-197; Zots and Buche 2000, p. 203), restricting them from a more widespread pre-glaciation distribution. Trichomanes punctatum ssp. floridanum is considered strongly hygrophilous (growing or adapted to damp or wet conditions) and generally perceived as restricted to constantly humid microhabitat (Krömer and Kessler 2006, p. 57). T. p. ssp. floridanum occurs only in the U.S. in the State of Florida. In Florida, T. p. ssp. floridanum is only known to occur in Miami-Dade and Sumter Counties.

Both extant metapopulations live in dense canopy habitats, with shady conditions that may be obligatory due to the poikilohydric (i.e., possess no mechanism to prevent desiccation) nature of some fern species (Krömer and Kessler 2006, p. 57). The canopy directly contributes to the surrounding humidity of an area. Dense canopies found in rockland habitats can minimize temperature fluctuations by reducing soil warming during the day and heat loss at night. In areas with greater temperature variations, as in Sumter County, this temperature minimization effect can help prevent frost damage to the interior of the hammock (FNAI 2010, p. 25). Mesic conditions are further maintained by the hammock's rounded canopy profile, which deflects winds, limiting desiccation during dry periods and reducing interior storm damage (FNAI 2010, p. 25). Changes in the canopy can impact humidity and evaporation rates, as well as the amount of light available to the understory.

In Miami-Dade County, Trichomanes punctatum ssp. floridanum is generally epiphytic (a plant that grows non-parasitically upon another plant) or epipetric (growing on rocks), typically growing in rocky outcrops of rockland hammocks, in oolitic (composed of minute rounded concretions resembling fish eggs) limestone solution holes, and, occasionally, on tree roots in limestone-surrounded areas (Phillips 1940, p. 166; Nauman 1986, p. 180; Whitney et al. 2004, pp. 105-106; Possley 2013f, pers. comm.; van der Heiden 2014b, pers. comm.). These rockland habitats are outcrops primarily comprised of marine limestone representing the distinct geological formation of the Miami Rock Ridge, a feature which encompasses a broad area from Miami to Homestead, Florida, and narrows westward through the Long Pine Key area of Everglades National Park (ENP) (Snyder et al. 1990, pp. 233-234). Several endemic plant species have been identified to be closely associated with the rocklands of southern Florida; these plants are believed to have no adaptation for long-distance dispersal, suggesting a lengthy period of evolution on rocky substrate in southern Florida (Snyder et al. 1990, p. 236).

Rockland hammocks are a type of rich tropical hardwood hammock (forest) on upland sites in areas where limestone is very near the surface and often exposed. Once numerous throughout South Florida, these rockland hammocks have a diverse closed canopy and shrub layer, where more than 120 native tree and shrub species are known to occur, including a number of rare plant and animal species, federally listed and candidate species, South Florida endemics, and tropical species at or near the northern limit of their ranges (Phillips 1940, p. 166; Snyder et al. 1990, p. 16; Gann et al. 2009, p. 3). The forest floor is characterized by leaf litter with varying amounts of exposed limestone and has few herbaceous species. Rockland hammocks generally consist of larger, mature trees in the interior, while the margins can be almost impenetrable due to dense growth of smaller shrubs, trees, and vines (FNAI 2010, pp. 24-27). The canopy cover is typically very dense where Trichomanes punctatum ssp. floridanum occurs. In Miami-Dade County, the hammocks consist of a mix of temperate and tropical hardwood trees, both canopy and understory, including Ocotea coriacea (lancewood), Coccoloba diversifolia (pigeon plum), Quercus virginiana (live oak), Simarouba glauca (paradise tree), Ficus aurea (strangler fig), and Sideroxylon foetidissimum (mastic) (see Snyder et al. 1990, p. 241, for complete list). Soils where T. p. ssp. floridanum is extant in Miami-Dade County generally consist of an uneven layer of highly organic soil overlying rock (Snyder et al. 1990, p. 238); soils are classified as Matecumbe Muck (moderately well-drained soils that are very shallow) (Florida Geographic Data Library 2013, http://www.fgdl.org/​). Soils from historical and extant records consist of the following soil types: Krome Very Gravelly Loam, Cardsound Silty Clay Loam-Rock Outcrop Complex, Opalocka Sand-Rock Outcrop Complex, and Dania Muck.

The limestone solution holes consist of bare rock walls that are considered specialized habitat within these hammock areas that host Trichomanes punctatum ssp. floridanum, as well as several other fern species (Snyder et al. 1990, p. 247). The solution hole features that dominate the appearance of rock surface in the Miami Rock Ridge are steep-sided pits, varying in size, formed by dissolution of subsurface limestone followed by a collapse above (Snyder et al. 1990, p. 236). Limestone solution holes vary in size, from shallow holes less than 0.5 meter (m) (1.6 feet (ft)) deep to those that cover over 100 m² (1,076 ft²) and are several meters deep (Snyder et al. 1990, p. 238). The bottoms of most solution holes are filled with organic soils, while deeper solution holes penetrate the water table and have (at least historically) standing water for part of the year (Snyder et al. 1990, pp. 236-238). Humidity levels are higher in and around the solution holes because of standing water and moisture retained in the organic soils. Many tropical, epipetric plant species are associated with the sinkholes and solution holes in rockland hammocks.

In Sumter County, Trichomanes punctatum ssp. floridanum is known to be epipetric, residing on limestone boulders in high atmospheric humidity hammocks (van der Heiden 2013a, pers. comm). Plants live in a mesic hammock on limestone boulders 0.1-1.5 m (0.3-4.9 ft) tall (see “Current Range” section, below). Mesic hammock is a developed evergreen hardwood and/or palm forest on soils that are rarely inundated (FNAI 2010, pp. 19-23) and commonly associated with hydric hammock and mixed wetland hardwoods. The difference between mesic hammocks and surrounding habitats is a slight difference in elevation; mesic hammocks occur on higher ground within basin or floodplain wetlands, as patches of oak/palm forest in dry prairie or flatwoods communities, on river levees, or in ecotones (transition area between two biomes or areas of distinct plant and animal groups) between wetlands and upland communities and at the edges of lakes, sinkholes, other depressional or basin wetlands, and river floodplains where natural fires do not occur (FNAI 2010, pp. 19-23). Historically, mesic hammocks were thought to be restricted to naturally fire-protected areas such as islands and peninsulas of lakes.

Although there are several occurrences of Trichomanes punctatum ssp. floridanum in Sumter County where sunlight can be observed through the canopy, generally the habitat is shaded throughout the year, with the lowest amount of canopy cover recorded at 64 percent (van der Heiden and Johnson 2013, pp. 8, 20). T. p. ssp. floridanum has been observed growing on small limestone rocks, as well as boulders with tall, horizontal faces with numerous other species, including rare State-listed species (e.g., Asplenium cristatum (hemlock spleenwort)) and widespread Pecluma dispersa (widespread polypody) (van der Heiden 2013b, pers. comm.; van der Heiden and Johnson 2013, p. 7).

Within one occupied Sumter County hammock (Rocky Hammock), the majority of Trichomanes punctatum ssp. floridanum occur on the northern face of limestone boulders; however, those clusters found on non-north-facing limestone generally occur in close proximity to other boulders, trees, or within protected crevices (van der Heiden and Johnson 2014, p. 7). It has been suggested the northern aspect of limestone boulders are more often inhabited by this taxon because of the reduced exposure to sunlight, promoting cooler temperatures and higher moisture as compared to other sun-exposed sections of rock. This may also be the case for those clusters shielded by other boulders, by trees, or in crevices, allowing the plant to grow on any portion of the shielded rock as long as moisture levels remain high enough to prevent desiccation (van der Heiden and Johnson 2014, pp. 9-10). Additionally, both populations of T. p. ssp. floridanum in Sumter County grow within the northern quadrant of each hammock.

Soils of mesic hammock are sands mixed with organic matter, often containing a thick layer of leaf litter and generally well-drained. Although some areas maintain high moisture soils due to the accumulation of leaf litter and extensive canopy cover, in general, mesic hammocks can occur across a broad gradient of soil moisture conditions, from somewhat xeric to almost hydric soils. Rock outcrops may also occur in mesic hammocks, especially where limestone is near the surface (FNAI 2010, pp. 19-23). Soil types for the extant metapopulation of Trichomanes punctatum ssp. floridanum in Sumter County include Okeelanta Muck, Frequently Flooded, and Mabel Fine Sand (i.e., deep and very deep, somewhat poorly drained, slowly permeable soils that formed in sandy to clayey marine deposits, with a bouldery (abounding in rocks or stones) subsurface and 0-5 percent slopes (Florida Geographic Data Library 2013, http://www.fgdl.org/​)). Additionally, one historical record has Adamsville Fine Sand, Bouldery Subsurface, while another population containing a questionable record from an extirpated population has what is classified as Malabar Fine Sand, Frequently Flooded.

Plant communities associated with mesic hammocks vary depending on the latitude; tropical species gradually increase in frequency from the central to southern peninsular Florida. In south Florida, some high-elevation areas dry enough to support a semi-tropical mesic hammock do exist; however, most “high hammocks” are rockland hammocks occurring on limestone (FNAI 2010, pp. 19-23). Q. virginiana is common in mesic hammock communities. Oak species found in these hammocks tend to possess a broader tolerance of a range of conditions than do oaks in other habitats (FNAI 2010, pp. 19-23). Mesic hammocks do not contain wetland trees, as found in hydric hammocks; however, these two hammock types often occur as intermixed stands. Because mesic hammocks are often associated with hydric hammocks, with wetlands, or as a transition to uplands, they are sensitive to hydrologic alteration in the landscape. For example, changes in flooding frequency and/or duration can kill most mesic hammock tree species, while lowered water tables can shift vegetation towards xeric species or promote wildfires, destroying the hammock (FNAI 2010, pp. 19-23). Mesic hammocks may be distinguished from rockland hammocks by the dominance of temperate species in the canopy, whereas rockland hammocks are comprised of predominantly tropical woody species.

Trichomanes punctatum ssp. floridanum in Sumter County can be found under a dense canopy including Q. virginiana, Sabal palmetto (cabbage palm), Carpinus caroliniana (American hornbeam), Celtis laevigata (sugarberry), Acer negundo (boxelder), Liquidambar styraciflua (sweetgum), and Sapindus saponaria (wingleaf soapberry) (van der Heiden 2013c, pers. comm.; van der Heiden and Johnson 2014, pp. 7, 19). The hammocks where T. p. ssp. floridanum has been found are also surrounded by a mosaic of wetlands dominated by Taxodium distichum (cypress trees). Recent field surveys recorded 18 canopy species in Rocky Hammock and 12 in Tree Frog Hammock (van der Heiden and Johnson 2014, p. 19), both located in Sumter County. The average canopy closure for both populations in Sumter County has been estimated to be more than 75 percent, where it is heavily shaded, maintaining high humidity to reduce chances of desiccation (van der Heiden and Johnson 2014, p. 9). Van der Heiden and Johnson (2014, p. 9) speculate this dense, closed canopy can serve as a shield for T. p. ssp. floridanum to inhibit the growth of other plant species on the same part of an inhabited rock area.

Habitat differences between Miami-Dade and Sumter Counties have enabled this subspecies to adapt to very different conditions at each location. In Miami-Dade, where Trichomanes punctatum ssp. floridanum currently is found, the mean maximum temperature from the last 10 years (2004-2013) was 29.0 °C (84.3°F), and the mean minimum temperature for the same time period was 21.4 °C (70.5°F) (http://www1.ncdc.noaa.gov). In contrast, yearly mean temperatures were lower for Sumter County with 23.4 °C (74.2°F) recorded as the maximum temperature for the last 10 years (2004-2013), and 11.8 °C (53.2°F) as the minimum temperature for the same time period (National Oceanic and Atmospheric Administration 2014, http://www1.ncdc.noaa.gov). Although it is believed this subspecies needs high temperatures and humidity, along with dense canopy, the exact thresholds for these variables have yet to be determined.

Historical Range/Distribution

The historical range of Trichomanes punctatum ssp. floridanum included southern (Miami-Dade County; see Table 1, below) and central (Sumter County; see Table 2, below) Florida.

Miami-Dade County

In Miami-Dade, the range of this subspecies extended from Royal Palm Hammock (now in Everglades National Park (ENP)) at its southern limit, northeast to Snapper Creek Hammock, which is located in R. Hardy Matheson Preserve (derived from Gann et al. 2002, pp. 552-554), a range of at least 45 square kilometers (km²) (17 square miles (mi²)). Plants in Miami-Dade were known to historically occur in at least 11 hammocks: Deering-Snapper Creek Hammock, Castellow Hammock, Silver Palm Hammock (also known as Caldwell), Ross Hammock, Royal Palm Hammock (in ENP), Hattie Bauer Hammock, Shields Hammock, Nixon-Lewis Hammock, Fuchs Hammock, Addison Hammock (in the Deering Estate at Cutler), and Matheson Hammock. In the 1980s, T. p. ssp. floridanum was also documented in Meissner Hammock and Cox Hammock (now part of the tourist attraction “Monkey Jungle”) (Small 1918, p. 6; Small 1921, p. 211; Morton 1963 p. 90; Fairchild Tropical Garden 1968, p. 1; Nauman 1986 p. 182; Gann et al. 2002, pp. 552-554; Gann 2013, http://regionalconservation.org/​ircs/​database/​plants/​IRCSpAccount.asp?​TXCODE=​Tricpuncflor&​GENUS=​Trichomanes&​SPECIES=​punctatum&​Author=​Poir.&​INFRA1=​subsp.&​INFRA1NAME=​ ssp. floridanum&INFRA1AUTHOR=Wess.%20Boer&CommonNames=Florida%20bristle%20fern).

After the initial finding of Trichomanes punctatum ssp. floridanum in 1901, at Deering-Snapper Creek, J.K. Small made subsequent collections of the subspecies in and around Miami-Dade County including one in 1903, probably located in or near present-day Castellow Hammock (Gann 2014d, pers. comm.). Additional collections were obtained in 1903, in Castellow Hammock by A.A. Eaton with more recent observations by G. Gann and K. Bradley in the late 1990s (Bradley and Gann 1999), and J. Possley and others (Gann et al. 2002, pp. 552-554; Possley et al. 2013, pp. 43-45). T. p. ssp. floridanum was collected in Silver Palm Hammock in 1903, by A.A. Eaton and later reported again in 1980; however, this report was not confirmed. The fern was collected from Ross Hammock by J.K. Small and colleagues in 1906. Since then, part of this hammock has been destroyed, and what remains is currently protected as a Miami-Dade Conservation Area. In 1909, the subspecies was collected in Royal Palm Hammock (also known as Paradise Key), now within ENP, and later reported by W.E. Stafford in 1917 (Stafford 1919, p. 386; Gann et al. 2002, pp. 552-554).

Several collections of Trichomanes punctatum ssp. floridanum were made in Miami-Dade in 1915, including: Hattie Bauer Hammock, Shields Hammock, Nixon-Lewis Hammock, Fuchs Hammock, and Deering-Snapper Creek Hammock. Hattie Bauer Hammock, now a Miami-Dade County conservation area, has numerous subsequent collection records by Small (1915, 1916), Correll (1936), and McFarlin (1934, 1940) as cited by Gann 2013, http://regionalconservation.org/​ircs/​database/​plants/​IRCSpAccount.asp?​TXCODE=​Tricpuncflor&​GENUS=​Trichomanes&​SPECIES=​punctatum&​Author=​Poir.&​INFRA1=​subsp.&​INFRA1NAME=​ ssp. floridanum&INFRA1AUTHOR=Wess.%20Boer&CommonNames=Florida%20bristle%20fern. The last known collection in Hattie Bauer Hammock was recorded in 1960, by T. Darling, Jr., and subsequently reported as extirpated by Gann et al. (2002, pp. 552-554), until it was rediscovered in this hammock in 2011 by Possley (et al. 2013, pp. 1-2). Shields Hammock was destroyed prior to 1991 (Cressler 1991, Handwritten Notes). Fuchs Hammock is now part of the Fuchs Hammock Preserve (Gann et al. 2002, pp. 552-554) and was vouchered (pressed plant samples taken for future reference) again in 1954, by L. J. Brass; in 1959, by T. Darling Jr.; and in 1969, by F.C. Craighead (The Institute for Regional Conservation, Herbarium Specimens, Floristic Inventory of South Florida Database, September 12, 2007). Fuchs Hammock was also vouchered in 1993, following Hurricane Andrew (1992) by A. Cressler (Cressler 12 February 1993, handwritten notes,), and more recently observed by Possley and others over the years (Gann et al. 2002, pp. 552-554; Possley et al. 2013, pp. 43-45). T. p. ssp. floridanum was observed by G. N. Avery in 1983, in Meissner Hammock (immediately adjacent to Fuchs Hammock) and was since vouchered by K. Bradley in 1997 and 2002, and also observed by others (Gann et al. 2002, pp. 552-554; Possley et al. 2013, pp. 43-45).

In 1916, J.K. Small reported Trichomanes punctatum ssp. floridanum in Addison Hammock, now located within Deering Estate at Cutler, currently Miami-Dade County Park; however, these reports were never vouchered (J.K. Small 1916; Gann et al. 2002, pp. 552-554). Surveys in recent years have yet to find any populations of T. p. ssp. floridanum in Deering Estate at Cutler, Matheson Hammock, or Silver Palm Hammock (Possley 2013j, pers. comm.). The subspecies was last reported from Cox Hammock in 1989, by A. Cressler, where plants were observed in a sinkhole in the tourist attraction, “Monkey Jungle” (Cressler 1991, handwritten notes); it is not known if these plants still exist. Cox Hammock is located about 1.6 km (1.0 mi) northeast of Castellow Hammock Park. Additional hammocks existing today where the taxon formerly occurred include Ross and Royal Palm Hammock (in ENP) and Deering-Snapper Creek Hammock. A section of Deering-Snapper Creek Hammock was destroyed in 1912-1913, when the Snapper Creek Canal was constructed; dredging of this canal drastically altered the water table in the area, depleting the freshwater springs, while a large spoil berm from excavation of the canal destroyed existing habitat (Metro-Dade County Park and Recreation Department 1991, p. 10). Other hammocks in the historical range that are presumed destroyed include Nixon Lewis Hammock, which is partially destroyed (Gann 2013, http://regionalconservation.org/​ircs/​database/​plants/​IRCSpAccount.asp?​TXCODE=​Tricpuncflor&​GENUS=​Trichomanes&​SPECIES=​punctatum&​Author=​Poir.&​INFRA1=​subsp.&​INFRA1NAME=​ssp. floridanum&INFRA1AUTHOR=Wess.%20Boer&CommonNames=Florida%20bristle%20fern) and a station presumably near the Matheson Hammock Park vouchered by G. Peterson in 1940.

Table 1—Summary of Historical Reports, Population Locations, and Current Population and Hammock Status of Trichomanes Punctatum ssp. Floridanum in Miami-Dade County, Where Known

[Gann et al. 2002; The Institute for Regional Conservation, Herbarium Specimens, Floristic Inventory of South Florida Database, September 12, 2007; Florida Natural Areas Inventory element occurrences 9/12/2013; Possley 2013c, j-k, 2014a-c; Possley 2013, 2014 pers. comm.; Gann 2013, pers. comm.; van der Heiden 2013e, pers. comm.; Gann 2014a-f, pers. comm.; Gann et al. 2014, http://regionalconservation.org/​ircs/​database/​plants/​PlantPage.asp?​TXCODE=​Tricpuncflor]

No.	Population location	Year(s) of initial report(s)	Observer	Number of specimens collected	Current population status	Current hammock status
1	Deering-Snapper Creek Hammock (in R. Hardy Matheson Preserve)	1901 1915	J.K. Small, G.V. Nash J.K. Small, C.A. Mosier	3 1	Extirpated	Protected Area, Partially Destroyed.
2	Castellow Hammock	1903 1903	J.K. Small, J.J. Carter A.A. Eaton	2 4	Extant	Protected Area.
3	Silver Palm Hammock	1903	A.A. Eaton	1	Extirpated	Protected Area.
4	Ross Hammock	1906	J.K. Small, J.J. Carter	2	Extirpated	Protected Area, Partially Destroyed.
5	Royal Palm Hammock (ENP); aka Paradise Key	1909 1917	J.K. Small, J.J. Carter W.E. Stafford	2 None	Extirpated	Protected Area.
6	Hattie Bauer Hammock (Orchid Jungle)	1915 1915	J.K. Small, C.A. Mosier J.K. Small	2 3	Extant	Protected Area.
		1915	J.K. Small, C.A. Mosier, G.K. Small	5
		1916	J.K. Small	1
		1934	J.B. McFarlin	2
		1936	D.S. Correll	2
		1940	J.B. McFarlin	1
		1960	T. Darling Jr	1
7	Shields Hammock	1915	J.K. Small, C.A. Mosier, G.K. Small	1	Extirpated	Destroyed.
8	Nixon-Lewis Hammock	1915	J.K. Small, C.A. Mosier	1	Extirpated	Protected Area, Partially Destroyed.
9	Fuchs Hammock (Sykes Hammock)	1915 1954	J.K. Small, C.A. Mosier L.J. Brass	1 1	Extant	Protected Area.
		1959	T. Darling Jr	1
		1969	A.F. Clewell, F.C. Craighead	1
10	Addison Hammock (Deering Estate at Cutler)	1916	J.K. Small	None	Unknown 1	Protected Area.
11	Matheson Hammock Park	1940	G. Peterson	2	Unknown 2	Protected Area.
12	Meissner Hammock	1983	G.N. Avery	None	Extant	Protected Area.
13	Cox Hammock (Monkey Jungle)	1989	A. Cressler	None	Unknown 3	Privately Owned, Partially Destroyed.
1 Initial report is questionable.
2 Precise location of sample and associated report is questionable.
3 It is not known whether the species still occurs here.

Sumter County

In Sumter County, early collections and herbarium label data for Trichomanes punctatum ssp. floridanum are not accurate or precise in their location descriptions. The first documented collection in 1936, by R.P. St. John, simply states that T. p. ssp. floridanum was found 11.26 km (7.0 mi) east of Floral City. This collection is close to the extant populations in Sumter (in Rocky Hammock within Withlacoochee State Forest), which is east-southeast of Floral City, and is thought to be the location where T. p. ssp. floridanum existed on private land until it was cleared for cattle sometime after 1983. A specimen found 3 years later by J.B. McFarlin in 1939 was originally thought to be T. sphenoides; the herbarium label data described this collection as “South of Floral City, Florida. T. sphenoides is a misapplied synonym for T. p. ssp. floridanum according to FNAI. This is the only known station in the United States.” It is believed that these label data may have been incorrectly recorded, indicating a direction of south from Floral City, when it should have been east. In all likelihood, McFarlin's collection probably referred to the population in the Wahoo area, where St. John previously collected because he states his collection was from the same locality where it was originally found in 1936. The specimen found by McFarlin eventually led to reports of the taxon in Citrus County (Wherry 1964, p. 232; Nelson 2000, p. 81); however, this was never confirmed beyond the initial report. Systematic surveys have not been conducted in Citrus County; therefore, the only documented occurrences of T. p. ssp. floridanum in this region of Florida have been in Sumter County, just north of Wahoo and east of the Withlacoochee River.

Several years later, in 1954, R. Garrett collected Trichomanes punctatum ssp. floridanum southeast of Floral City. It is thought to be the same location where St. John and McFarlin made their previous collections; however, label data were again minimal and the exact location is uncertain. In 1959, T. Darling Jr. found this subspecies near Floral City, 11.26 km (7.0 mi) south near a location called Battle Slough. This record has never been confirmed because it is located on private property. Another specimen was found in 1963, by O. Lakela in an area known as Indian Field Ledges. Lakela recorded his location and collection to be west of Withlacoochee River off State Road #48. This information is believed to be incorrect based on a site visit by Darling (1961, p. 7), stating that the Indian Field Ledges is north of Wahoo, a locality east of the Withlacoochee River. T. p. ssp. floridanum was not found again in Sumter County until 1983, when S.W. Leonard made a collection on private property known as Rocky Point, north of Wahoo. This is presumed to be the same location where St. John, McFarlin, and Garrett collected their specimens, which is now extirpated.

Table 2—Summary of Historical Reports, Population Locations, and Current Population and Hammock Status of Trichomanes punctatum ssp. floridanum in Sumter County, Where Known

[Gann et al. 2002; The Institute for Regional Conservation, Herbarium Specimens, Floristic Inventory of South Florida Database, September 12, 2007; Florida Natural Areas Inventory Element Occurrences 9/12/2013; van der Heiden 2013d, 2014a, pers. comm.; Gann et al. 2014, http://regionalconservation.org/​ircs/​database/​plants/​PlantPage.asp?​TXCODE=​Tricpuncflor]

No.	Population location	Year of initial report	Observer	Number of specimens collected	Current population status	Current hammock status
1	11.26 km (7 mi) East of Floral City 1	1936	R.P. St. John	1	Presumed Extirpated	Privately Owned, Presumed Destroyed.
2	Floral City Area 1	1939	J.B. McFarlin	1	Unknown 2	Unknown.
3	Southeast of Floral City 1	1954	R. Garret	1	Presumed Extirpated	Privately Owned, Presumed Destroyed.
4	Floral City, 11.26 km (7 mi) south (Battle Slough) 1	1959	T. Darling Jr	1	Unknown 2	Privately Owned, Unknown.
5	East of Withlacoochee River, off State Road #48 (Indian Field Ledges) 1	1963	O. Lakela	1	Extirpated	Protected Area.
6	Rocky Point, (north of Wahoo)	1983	S.W. Leonard	1	Extirpated	Privately Owned, Destroyed.
1 Sumter County collections and herbarium label data for Trichomanes punctatum ssp. floridanum are inaccurate in location descriptions.
2 Initial report is questionable.

Current Range

The extant metapopulation of Trichomanes punctatum ssp. floridanum in Miami-Dade County is approximately 400 km (249 mi) south of the extant metapopulation in Sumter County. Both metapopulations of T. p. ssp. floridanum are located entirely on public lands (see Table 3, below).

Miami-Dade County

The four populations that constitute the Miami-Dade County metapopulation are located in urban preserves managed by the County's Environmentally Endangered Lands (EEL) Program (see Factor A, Conservation Efforts to Reduce Habitat Destruction, Modification, or Curtailment of Its Range, below). These EEL properties include: Castellow Hammock Park (39.5 hectares (ha)) (97.6 acres (ac)), Hattie Bauer Hammock (5.7 ha (14.0 ac)), Fuchs Hammock Preserve (15.7 ha (38.8 ac)), and Meissner Hammock (4.1 ha (10.1 ac)). Three of these preserves (76 percent of the land area) are owned by the County; the fourth, Meissner Hammock (24 percent), is owned by the State and leased to the County (Dozier 2014, pers. comm.). The subpopulations in Fuchs Hammock include a new population that was found in July 2013 (Possley et al. 2013, pp. 43-45). Fuchs and Meissner Hammocks are immediately adjacent to each other, and Castellow Hammock Park is 10.5 km (6.5 mi) to the northeast. During 2011, another population was re-discovered at Hattie Bauer Hammock (8 ha (20 ac)) (Possley et al. 2013, pp. 43-45). Hattie Bauer Hammock is 4.02 km (2.5 mi) south of Castellow Hammock and approximately 8.05 km (5 mi) northeast of Fuchs and Meissner Hammocks. In general, Trichomanes punctatum ssp. floridanum occurs in small areas within each hammock.

No comprehensive survey has been conducted in rockland hammocks in Miami-Dade County where suitable Trichomanes punctatum ssp. floridanum habitat has been identified. Although these areas have been extensively explored by numerous botanists and plant enthusiasts, including sites where the subspecies was formerly found, due to the cryptic nature of this plant it may have been overlooked and new occurrences may yet be discovered (Possley 2013f, pers. comm.; van der Heiden 2013c, pers. comm.). Surveys conducted in the late 1990s, and as late as 2010, did not find T. p. ssp. floridanum in Silver Palm Hammock (Gann et al. 2002, pp. 552-554; Possley 2013g, pers. comm.). A plant sample was collected in Nixon-Lewis Hammock by Small and Mosier in 1915; however, due to extensive disturbance of this hammock, subsequent surveys conducted in 2006, by IRC, could not find the taxon (Bradley and Gann 2005, unpublished data). Over the years, IRC has completed systematic surveys in ENP in Royal Palm Hammock and other hammocks on Long Pine Key; however, plants have not been found there (Gann et al. 2009; pp. 1-66). In 2003, based on historical records, staff from ENP and IRC surveyed Royal Palm Hammock for T. p. ssp. floridanum without success; subsequent surveys conducted in rockland hammocks throughout Long Pine Key (in ENP) for other rare plants were also not successful in finding T. p. ssp. floridanum (Sadle 2013, pers. comm.).

Sumter County

The Sumter County metapopulation consists of two extant populations of Trichomanes punctatum ssp. floridanum that have been reported north of Wahoo, in the Withlacoochee State Forest's Jumper Creek Tract; these populations are located in Rocky Hammock (located on 44 boulders) and Tree Frog Hammock (located on 4 boulders) (van der Heiden and Johnson 2014, p. 7). The population in Tree Frog Hammock was discovered as recently as April 2013, during regional surveys (van der Heiden 2013c, pers. comm.). Two additional populations were known from private land just south of the State Forest; however, these populations were subsequently extirpated due to the clearing of land for agriculture by the property owner (van der Heiden 2013c, pers. comm.).

Recent GIS analyses show the soil type associated with known extant occurrences of Trichomanes punctatum ssp. floridanum in the northern metapopulation to be Okeelanta Muck, Frequently Flooded; this soil covers approximately 1,478 ha (3,652 ac) in Sumter County. However, not all of these areas have been systematically surveyed. Although surveys conducted of a boulder field within Withlacoochee State Forest's Jumper Creek Tract (called the Indian Field Ledges) in August 2007 and April 2013 were unsuccessful (van der Heiden 2013c, pers. comm.), the discovery of new populations may be possible in the area. Indeed, the population of this subspecies in Jumper Creek's Tree Frog Hammock is a new population that was discovered in April 2013, during additional hammock surveys within Withlacoochee State Forest and the surrounding area (van der Heiden 2013c, pers. comm.).

It is also possible that other subpopulations may exist in Sumter County. Indian Ledges, a hammock located on private land near Jumper Creek (not to be confused with Indian Field Ledges), just north of Wahoo, is believed to be suitable for Trichomanes punctatum ssp. floridanum, including a dense canopy and appropriate soil (Deangelis 2014a-b, pers. comm.). Over the years, many rare ferns and orchids have been observed in the Indian Ledges Hammock; unfortunately, this hammock was heavily damaged by hurricanes in 2004 (Deangelis 2014a, pers. comm.).

Portions of the Southwest Florida Water Management District (SWFWMD) property within the Green Swamp more than 40.23 km (25 miles) southeast of the Jumper Creek Tract in Withlacoochee State Forest (WSF) may also contain appropriate habitat for Trichomanes punctatum ssp. floridanum based on existing habitat features such as dense canopy, high humidity microclimates, mesic hammock, and limestone outcroppings (Elliott 2014, pers. comm.). The SWFWMD property within the Green Swamp is the only area where land alteration has not occurred in Sumter County (11,343 ha (28,030 ac)). Portions of Green Swamp owned by the SWFWMD also extend into three other counties: Lake, Polk, and Pasco. Future survey efforts coordinating with local land owners and conservation organizations in this area may prove successful in finding new populations of T. p. ssp. floridanum.

Table 3—Summary of Known Extant Occurrences of Trichomanes punctatum ssp. floridanum. (Possley 2013, p. 1-2; Dozier 2014, pers. comm.; van der Heiden and Johnson 2014, pp. 1-3).

Metapopulation location (County)	Population location	Land ownership	Number of subpopulations	Status
Miami-Dade	Meissner Hammock	State	2	Extant.
Miami-Dade	Fuchs	County	4	Extant.
Miami-Dade	Castellow	County	3	Extant.
Miami-Dade	Hattie Bauer	County	1	Extant.
Sumter	Rocky Hammock, Withlacoochee State Forest's Jumper Creek Tract	State	1	Extant.
Sumter	Tree Frog Hammock, Withlacoochee State Forest's Jumper Creek Tract	State	1	Extant.

Population Estimates and Status

Trichomanes punctatum ssp. floridanum grows in dense mats and is rhizomatous (a horizontal stem that often sends out roots and shoots from its nodes). Fronds are scattered in matted clusters along the stems, making it difficult to count clusters, or groups of plants in the same location, and nearly impossible to accurately count individual plants (Nelson 2000, p. 79). This issue has been encountered in other Trichomanes species, such as Trichomanes boschianum (Appalachian bristle fern) (Hill 2003, p. 11). As such, populations are typically described by the number of clusters (i.e., groups of plants in various sinkholes, on tree roots, on boulders) and the total area covered by the cluster.

Miami-Dade County

In Miami-Dade County, there are four populations of the fern with a total of 10 subpopulations (i.e., nine solution holes and one rocky outcropping). Overall, this taxon occurs in small areas (i.e., less than 0.5 ha (1.2 ac)) at each site, with 88 percent of the total area in three subpopulations in Castellow Hammock. Recent surveys (see Table 4, below) in Miami-Dade by Fairchild (Possley 2013 pp. 1-2) found the fern covering a total area of approximately 9.92 m² (106.56 ft ²) (Possley 2013, pp. 1-2).

Table 4—Area covered by each of 10 known subpopulations of Trichomanes punctatum ssp. floridanum in Miami-Dade County, October and November 2013 (Possley 2013, pp. 1-2) and in Sumter County, December 2013 (van der Heiden and Johnson 2014, pp. 7, 14)

Metapopulation	Population	Subpopulation	Estimated area covered (m2)	Number of clusters
Miami-Dade	Hattie Bauer Hammock	Hole (no tag)	0.078	2-10
Miami-Dade	Fuchs Hammock	Hole 532	0.017	2-10
Miami-Dade	Fuchs Hammock	Hole 533	0.038	2-10
Miami-Dade	Fuchs Hammock	Hole 1431	0.128	2-10
Miami-Dade	Fuchs Hammock	Root 1430	0.047	1
Miami-Dade	Meissner Hammock	Hole 2319	0.145	2-10
Miami-Dade	Meissner Hammock	Hole 3337	0.713	2-10
Miami-Dade	Castellow Hammock	Hole 2332	4.688	11-100
Miami-Dade	Castellow Hammock	Hole 2331	3.925	11-100
Miami-Dade	Castellow Hammock	Hole 944	0.141	2-10
Miami-Dade County Total			9.920 m2
Sumter	Rocky Hammock	N/A	4.355	44
Sumter	Tree Frog Hammock	N/A	0.132	4
Sumter County Total			4.487 m2
Total Area Covered			14.407 m2

The largest known population of Trichomanes punctatum ssp. floridanum in Miami-Dade County is located at Castellow Hammock (Possley et al. 2013, p. 43), where it occurs in three of the larger subpopulations. In October of 2011, field surveys revealed extensive desiccation of this population after intensive nonnative vegetation removal (Possley 2013h, pers. comm.); however, by November 2013, these plants had recovered, and the total area covered by all clusters (i.e., two or more plants next to each other) was estimated at 8.754 m² (94.227 ft²). Meissner Hammock has two subpopulations; the clusters in this hammock cover an area of 0.858 m² (9.235 ft²) and are considered healthy, with no signs of desiccation (Possley et al. 2013, pp. 43-45). There is one subpopulation in Hattie Bauer Hammock covering approximately 0.78 m² (8.4 ft²) and three subpopulations of T. p. ssp. floridanum at Fuchs Hammock, with an additional one that was discovered in July 2013, totaling an area of 0.230 m² (2.476 ft²) (Possley 2013, pp. 1-2; Possley et al. 2013, pp. 43-45).

Sumter County

In Sumter County, the Rocky Hammock subpopulation contains 44 clusters, while the newly discovered subpopulation (Tree Frog Hammock) is much smaller with only 4 clusters observed (van der Heiden and Johnson 2014, p. 7). Average cluster size for Rocky Hammock is estimated at 4.355 m² (46.877 ft²) and 0.132 m² (1.421 ft²) for Tree Frog Hammock.

Summary of Factors Affecting the Species

Section 4 of the Act (16 U.S.C. 1533), and its implementing regulations at 50 CFR part 424, set forth the procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, we may list a species based on one or more of the following five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. Listing actions may be warranted based on any of the above threat factors, singly or in combination. Each of these factors as applied to Trichomanes punctatum ssp. floridanum is discussed below.

Information pertaining to Trichomanes punctatum ssp. floridanum in relation to the five factors provided in section 4(a)(1) of the Act is discussed below. In considering what factors might constitute threats, we must look beyond the mere exposure of the species to the factor to determine whether the species responds to the factor in a way that causes actual impacts to the species. If there is exposure to a factor, but no response, or only a positive response, that factor is not a threat. If there is exposure and the species responds negatively, the factor may be a threat, and we then attempt to determine if that factor rises to the level of a threat, meaning that it may drive or contribute to the risk of extinction of the species such that the species warrants listing as an endangered or threatened species as those terms are defined by the Act. This does not necessarily require empirical proof of a threat. The combination of exposure and some corroborating evidence of how the species is likely impacted could suffice. The mere identification of factors that could impact a species negatively is not sufficient to compel a finding that listing is appropriate; we require evidence that these factors are operative threats that act on the species to the point that the species meets the definition of an endangered or threatened species under the Act.

Factor A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range

Habitat modification and destruction, caused by human population growth and development, agricultural conversion, regional drainage, and canal installation, have impacted the range and abundance of Trichomanes punctatum ssp. floridanum. Secondary effects from hydrology and canopy changes have resulted in changes in humidity, temperature, and existing water levels; loss of natural vegetation; and habitat fragmentation. The modification and destruction of habitat where T. p. ssp. floridanum was once found have been extreme in most areas of Miami-Dade County; while they have been less dramatic in Sumter County, clearing of land for agricultural conversion and historical logging has resulted in very few areas where the habitat has not been modified. These threats are discussed in detail below.

Human Population Growth, Development, and Agricultural Conversion

Miami-Dade County-Rockland hammocks are considered imperiled both locally and globally, with a limited distribution and an FNAI ranking of G2 (imperiled globally because of rarity (6 to 20 occurrences or fewer than 3,000 individuals) or because of vulnerability to extinction due to some natural or manmade factor))/S2 (either very rare and local in Florida (21-100 occurrences or fewer than 10,000 individuals) or found locally in a restricted range or vulnerable to extinction from other factors)) (FNAI 2010, pp. 24-26, FNAI 2013, http://www.fnai.org/​PDF/​NC/​Rockland_​Hammock_​Final_​2010.pdf). The tremendous development and agricultural pressures in the rapidly urbanizing rockland hammock areas in south Florida have resulted in significant reductions of this habitat type, which is also susceptible to fire, frost, canopy disruption, and groundwater reduction (FNAI 2010, pp. 24-26).

Extensive land clearing for human population growth and development in Miami-Dade County has altered, degraded, or destroyed hundreds of acres of this once abundant rockland hammock ecosystem. Rockland hammocks once occurred across the Miami-Rock Ridge, usually in association with pine rocklands, or the edges of marl prairies (areas of thin, calcitic soil that has accumulated over limestone bedrock) or tidal swamps (Service 1999, p. 122). Destruction of rocklands, including rockland hammocks, has occurred since the beginning of the 1900s. Historical impacts to the environment were addressed by Small (1938, p. 50), who called attention to the demise of Trichomanes punctatum ssp. floridanum from habitat destruction, and Phillips (1940, p. 167) who expressed his concern for south Florida hammocks due to the obvious and vast amount of destruction of land in the region. Early settlers in Florida cleared hammocks for residential development, farming, and range for livestock, while industrial logging also occurred in the region (Snyder et al. 1990, pp. 271-272). Consistent burning of pinelands in Miami-Dade also encroached upon adjacent hammocks, as in the case of Castellow Hammock (Phillips 1940, p. 167). Habitat impacts were further exacerbated by natural stochastic events, such as the hurricane in 1935 that destroyed Ross Hammock (Phillips 1940, p. 167).

Rockland hammock habitat is now limited to public conservation lands where future development and habitat alteration are less likely than on private lands. However, these lands could be sold off in the future and become more likely to be developed or altered in a way that negatively impacts the subspecies and its habitat. Additionally, rockland hammock may be found on private lands; however, the fate of this existing habitat is unknown, as it is dependent upon actions of individual property owners (see discussion under Factor D).

Due to the possibility that additional populations of Trichomanes punctatum ssp. floridanum may be found on private property and could be destroyed, and the fact that there are no guarantees that the limited rockland hammock habitat will remain as public conservation land in perpetuity, habitat loss due to population growth, development, and agricultural conversion poses a threat to this subspecies in Miami-Dade County.

Sumter County—In Sumter County, human population growth and development has occurred, but to a lesser degree than in Miami-Dade County; however, Sumter County has a long history of agriculture dating back to the early 1860s. Generally speaking, all land that was feasible for agriculture was cleared at some point. In particular, mesic hammocks where Trichomanes punctatum ssp. floridanum occurs have experienced disturbances from human activities such as logging, understory clearing, cattle grazing, and introduction of feral hogs. These natural mesic canopies and soils have largely been destroyed due to their desirable locations for living, camping, and recreating. The global and State rank for mesic hammock habitat (G3/S3) signifies it is considered to have a restricted range or be vulnerable to extinction from other factors (FNAI 2010, p. 22).

Concerns exist regarding future population growth and development in those communities remaining in Sumter County and on lands where urbanization and agriculture have not yet been established. According to the Sumter County Comprehensive Plan, a growth management paradigm has been developed that focuses public resources on urban areas to protect existing undeveloped land for agricultural use (Sumter County 2012, Data and Analysis section). Currently, the threat with greatest impact to T. p. ssp. floridanum habitat in Sumter County is the potential for agricultural and residential clearing of mesic hammocks on small, fragmented private parcels and in existing conservation areas.

Privately owned land in the area around Wahoo where Trichomanes punctatum ssp. floridanum is found has been zoned as “agricultural” on the Sumter County Future Land Use Map (Sumter County 2012, p. 42). The County exempts single site residential development and agriculture from environmental review and does not regulate land clearing for a single residence. Therefore, any undocumented populations and suitable habitat on private lands are at risk due to land-clearing activities, agricultural conversions, and development. For example, one Sumter County subpopulation observed in 1999 on private land was extirpated due to pasture clearing on the property for livestock (van der Heiden 2013c, pers. comm.). Although undeveloped land is more abundant in Sumter County than in Miami-Dade County, the fact that no virgin land remains within Sumter County may reduce the likelihood of new populations being discovered (Farnsworth 2013, pers. comm.). A full survey for T. p. ssp. floridanum and associated suitable habitat is needed in Sumter County to determine the severity of potential habitat loss on this subspecies regionally, including the potential impact from future human population growth and development.

Due to existing agricultural and residential clearing of mesic hammocks and potential future clearing on private lands and within existing conservation areas, habitat loss due to human population growth, development, and agricultural conversion poses a threat to T. p. ssp. floridanum in Sumter County.

Regional Drainage and Consumptive Use

Miami-Dade County—Landscape-level drainage has been extensive in Miami-Dade County. In the early 1900s, drainage initiatives were undertaken to modify land for agriculture and development; impacts resulted in a region-wide drop in the water table (Nauman 1986, p. 182; Lodge 2005, p. 222), disturbing rockland hammocks and their flora (Service 1999, pp. 3-138), including Trichomanes punctatum ssp. floridanum. Additional stress from regional drainage for canal construction has also contributed to the extirpation and decline of this metapopulation (Nauman 1986, p. 182; see also “Historical Range/Distribution”, Miami-Dade County section, above). As a consequence of the pervasive drainage throughout Miami-Dade County, solution holes, which often contained standing water during the rainy season, now hold much less, if any, water during much of the year, resulting in decreased ambient humidity levels (Phillips 1940, p. 171; Nauman 1986, p. 182; Adimey 2013a, field notes). Even though regional changes in hydrology have not caused extirpation of T. p. ssp. floridanum at most locations, they may have already induced stress by promoting vulnerability to other stressors, such as periodic long-term droughts, cold weather exposure, and other stochastic events. Furthermore, groundwater levels in the vicinity of T. p ssp. floridanum are not targeted as part of the Comprehensive Everglades Restoration Plan (CERP) (a framework and guide to restore, protect, and preserve the water resources of central and southern Florida, including the Everglades), and, therefore, impacts from regional drainage are not expected to be ameliorated by CERP. Rockland hammocks in Miami-Dade County have been modified as a result of hydrology changes, reducing the amount of water available to these habitats. This is an ongoing threat for T. p. ssp. floridanum, as hammocks on limestone substrates are dependent on the underlying water table to keep humidity levels high, especially in limestone sinkholes (Service 1999, pp. 3-127).

Currently, the human population in Miami-Dade County is expected to grow to more than 4 million by 2060, an annual increase of roughly 30,000 people (Zwick and Carr 2006, p. 20). Although water demands will continue to rise with population increases, the extent of future impacts on existing habitat and the metapopulation of Trichomanes punctatum ssp. floridanum in Miami-Dade County is unknown at this time.

Sumter County—In Sumter County, water drawdowns have historically been minimal; regional modeling conducted by SWFWMD indicates less than a 0.06-m (0.2-ft) current use of water in the Upper Floridan Aquifer (Deangelis 2014a, 2014c, pers. comm.). No surface water withdrawals are currently occurring in Sumter County; however, it is possible in the future. Minimum flows and levels (MFLs), which are water withdrawal standards to limit water use set the by regional Water Management Districts (WMDs), are already established for the Withlacoochee River portion of the Withlacoochee River watershed in Sumter County. Although increases in human population and development in Sumter County may increase water table use, it is believed changes due to drought conditions (e.g., on the order of several feet) will have a far greater impact on the hydrology (Deangelis 2013a, pers. comm.).

Hydrology

Hydrology is a key ecosystem property that affects distribution and viability of rare plants (Gann et al. 2009, p. 6). Hydrology changes have extensively modified and, in some cases, destroyed habitat in south Florida. As a result of human population growth, development, agricultural conversion, and regional drainage, the hydrology of Trichomanes punctatum ssp. floridanum habitat has changed drastically and has contributed to the alteration in ambient humidity and temperature.

As a hygrophilous (living or growing in damp places) subspecies thought to be restricted to a consistent humid microhabitat (Krömer and Kessler 2006, p. 57), high humidity is a critical factor to its survival; any habitat modification or destruction that changes ambient humidity levels is believed to be a threat to this subspecies (Nauman 1986, p. 182). As noted above, drainage efforts implemented in south Florida have significantly reduced historical water table levels, altering ambient humidity in the area. It is speculated that this subspecies may be living in discrete areas where humidity may be at the threshold for T. p. ssp. floridanum to survive. Minor drops in ambient humidity may limit reproduction and can negatively impact overall health of existing metapopulations, as well as inhibit the growth of new plants, impacting long-term viability (van der Heiden, 2013c, pers. comm.; Possley 2013f, pers. comm.). Van der Heiden and Johnson (2013, p. 9) recently observed this in Sumter County where small drops in ambient temperature and humidity resulted in observed declines in the health of some clusters of T. p. ssp. floridanum within the local population.

Canopy Changes

Canopy is also an important habitat feature for Trichomanes punctatum ssp. floridanum, and in most cases, is the primary factor controlling surrounding temperature and humidity levels that are critical to the survival of this subspecies The proper amount of high shade and low light is critical for the persistence of this subspecies; these features help to maintain humidity and avoid desiccation from excessive light exposure (van der Heiden 2013c, pers. comm.; Possley 2013f, pers. comm.; Adimey 2013a-b, field notes). Currently, in both metapopulations, dense canopy cover is a necessity; however, the lower limits of canopy density needed to ensure survival are not yet known. Changes to existing canopies can result from land clearing and conversion, natural stochastic events, competition with nonnative species, and nonnative species control (see discussion under Factor E).

Historically, as land was developed, natural features of the landscape changed, directly eliminating Trichomanes punctatum ssp. floridanum and also eliminating surrounding vegetation and habitat features essential to this subspecies. Field observations in Miami-Dade County have found clusters of T. p. ssp. floridanum desiccated when the immediate canopy above the ferns was destroyed or substantially reduced, allowing high amounts of light into the understory (Possley 2013h, pers. comm.); however, over the course of many months, these clusters eventually recovered.

The loss of canopy can result in plant desiccation via increased sun and wind exposure, increased ambient temperatures, changes in ambient humidity, and the proliferation of exotic species (see Factor E discussion, below). Destruction or changes in canopy of any existing populations could result in elimination of an entire population. Therefore, canopy loss is believed to be a limiting factor for the future persistence of the subspecies and is therefore considered a threat to T. p. spp. floridanum.

Habitat Fragmentation

Habitat fragmentation limits dispersal and population size, and promotes vulnerability among existing populations. In Miami-Dade County, most remaining Trichomanes punctatum ssp. floridanum habitat (i.e., Fuchs, Meissner, Castellow, Hattie Bauer hammocks) is surrounded by housing development and agricultural land, resulting in scattered and small, fragmented natural areas. Regional drainage and hydrology changes may also have contributed to the fragmented habitat in Miami-Dade County. In Sumter County, the impacts of habitat fragmentation are not as severe, as conservation lands are on large, adjacent tracts. Future development in Sumter County could result in an increase in fragmented habitat and pose a threat for this northern metapopulation (van der Heiden 2013c, pers. comm.). However, thorough knowledge of the impacts and subsequent consequences from habitat fragmentation is unknown for both metapopulations of Trichomanes punctatum ssp. floridanum because information and understanding of dispersal mechanisms for this subspecies is currently lacking. The best available data regarding the impacts of habitat fragmentation on other plant species suggests that habitat fragmentation is likely a stressor impacting this subspecies but does not indicate that it rises to the level of a threat.

Conservation Efforts To Reduce Habitat Destruction, Modification, or Curtailment of Its Range

Conservation efforts to reduce habitat destruction are generally focused on the conservation of land in which both metapopulations occur. All known extant populations occur on State- or County-owned land that is currently protected from future development. In Miami-Dade County, extant occurrences of Trichomanes punctatum ssp. floridanum have been protected through acquisition within the County's EEL Program (http://www.miamidade.gov/​environment/​endangered-lands.asp).

Fee Title Properties

In 1990, Miami-Dade County voters approved a 2-year property tax to fund the acquisition, protection, and maintenance of natural areas by the EEL Program. The EEL Program purchases and manages natural lands for preservation. Land uses deemed incompatible with the protection of the natural resources are prohibited by current regulations; however, the County Commission ultimately controls what may happen with any County property, and land use changes may occur over time (Gil 2013b, pers. comm.). To date, the Miami-Dade County EEL Program has acquired a total of approximately 95 ha (236 ac) of tropical hardwood and rockland hammocks (Gil 2013b, pers. comm.). The EEL Program also manages approximately 639 ha (1,578 ac) of tropical hardwood and rockland hammocks owned by the Miami-Dade County Parks, Recreation and Open Spaces Department, including some of the largest remaining areas of tropical hardwood and rockland hammocks (e.g., Matheson Hammock Park, Castellow Hammock Park, and Deering Estate Park and Preserves). A precursor to the EEL Program is the EEL Covenant Program, which regulates private lands for conservation through easements.

EEL Covenant Program

In 1979, Miami-Dade County enacted the EEL Covenant Program, which reduces taxes for private landowners of natural forest communities (NFC) such as pine rocklands and rockland hammocks. Under the EEL Covenant Program, landowners agree not to develop their property and manage it for a period of 10 years, with the option to renew for additional 10-year periods (Service 1999, pp. 3-177). The EEL Covenant Program currently regulates approximately 119 rockland hammock properties, comprising approximately 315.65 ha (780 ac) of habitat (Joyner 2013b, pers. comm.).

Although these temporary conservation easements provide valuable protection for their duration, they are not considered under Factor D, below, because they are voluntary agreements and not regulatory in nature. Miami-Dade County currently has approximately 21 rockland hammocks properties enrolled in this program, preserving 20.64 ha (51 ac) of rockland hammock habitat (Joyner 2013b, pers. comm.). The vast majority of these properties are small, and many are in need of habitat management, such as removal of nonnative, invasive plants. Although the EEL Covenant Program has the potential to provide valuable habitat for unknown or future populations of Trichomanes punctatum ssp. floridanum, the actual contribution of these designated conservation lands is largely determined by whether individual landowners follow prescribed EEL management plans and NFC regulations (see “Local” under Factor D below).

These County- and State-owned land areas are critical to protecting Trichomanes punctatum ssp. floridanum, as well as other native flora in Florida. Conservation efforts to prevent the future extirpation of T. p. ssp. floridanum and other fern species in Miami's EEL Preserves have been underway for many years. In Miami-Dade County, conservation lands are and have been monitored by Fairchild and IRC, in coordination with the EEL Program, to assess habitat status and determine any changes that may pose a threat to or alter the abundance of T. p. ssp. floridanum (Possley 2013m, pers. comm.; van der Heiden 2013f-h, pers. comm.). Impacts to habitat (e.g., canopy) via nonnative species and natural stochastic events are monitored and actively managed in areas where the taxon is known to occur. These programs are long-term and ongoing in Miami-Dade County; however, programs are limited by the availability of annual funding.

To date, only one reintroduction of filmy ferns (no specific species was indicated) was attempted by F.C. Craighead in the early 1960s, in several hammocks within ENP within the Long Pine Key area; these efforts were unsuccessful without further explanation (Gann 2013, http://regionalconservation.org/​ircs/​database/​plants/​IRCSpAccount.asp?​TXCODE=​Tricpuncflor&​GENUS=​Trichomanes&​SPECIES=​punctatum&​Author=​Poir.&​INFRA1=​subsp.&​INFRA1NAME=​ ssp. floridanum&INFRA1AUTHOR=Wess.%20Boer&CommonNames=Florida%20bristle%20fern). This is not surprising since within-range reintroductions into unoccupied habitat have historically resulted in low success rates for plants (Maschinski et al. 2011, p. 159). Future reintroduction efforts will likely be attempted by MSBG from Trichomanes punctatum ssp. floridanum plants grown in-vitro from CREW.

In Sumter County, monitoring and management in Withlacoochee State Forest is provided through the Florida Forest Service (Werner 2013e, pers. comm.). Habitat is assessed annually for canopy changes that may alter ambient humidity levels and for impacts from nonnative plant species and feral pigs. Additionally, surveys on SWFWMD property are conducted periodically to assess habitat and search for rare plant species in the area (Deangelis 2013b, pers. comm.).

Summary of Factor A

Past human actions have destroyed, modified, and curtailed the range and habitat available for Trichomanes punctatum ssp. floridanum. Human population growth and development, agricultural conversion, and regional drainage have modified, or in most cases, destroyed, habitat where T. p. ssp. floridanum once occurred, thereby limiting the subspecies' current range and abundance in Florida.

In Miami-Dade County, habitat modification and destruction have severely impacted rockland hammocks that were once abundant. The Trichomanes punctatum ssp. floridanum metapopulation in Miami-Dade County is currently composed of four known populations, all on County-managed conservation lands. Historically, T. p. floridanum was found in an additional nine hammocks in Miami-Dade County. These populations have been extirpated, and the historical range of the southern metapopulation has been reduced by nearly 80 percent. Although much of the habitat has been destroyed and those fragments suitable for the plant remain protected in Miami-Dade County, habitat loss and modification from future development or conversion on private and conservation lands in Miami-Dade County poses a threat. In addition, the areas where T. p. floridanum currently exists are still vulnerable to activities in the surrounding areas including agricultural clearing and hydrologic alterations.

The Sumter County metapopulation of Trichomanes puctatum ssp. floridanum is composed of two known populations, both on State-owned land in the Jumper Creek Tract of the WSF. In central Florida, the subspecies was historically found in as many as seven additional locations. All of these historical populations have since been extirpated primarily due to land conversion and clearing (including for cattle grazing) and the impacts of local and regional drainage. Land clearing and hydrological alterations on private lands adjacent to the Jumper Creek Tract continues to be a threat to T. p. floridanum populations and habitat. Although historical habitat modification and destruction in Sumter County has not been as extensive as in South Florida, this is a future potential threat due to the large areas of undeveloped lands within Sumter County.

The destruction and modification of habitats have resulted in changes in canopy, humidity, hydrology, and fragmentation that have contributed to the declines of this taxon. High humidity and dense canopy cover are critical for Trichomanes puctatum ssp. floridanum' s survival; therefore, any habitat modification or destruction that changes ambient humidity levels or canopy cover poses a threat to this subspecies. Thorough knowledge of the impacts of habitat fragmentation is unknown for both metapopulations of T. p. ssp. floridanum because information on dispersal mechanisms of this subspecies is currently lacking. Habitat fragmentation is likely a stressor impacting this subspecies, but the best available data do not indicate that it rises to the level of a threat. Water withdrawals may still be of some concern; however, the impact of this factor is not currently known, and therefore, we have determined it to be a stressor, but it is not rising to the level of a threat at this time.

Conservation efforts are currently providing some benefits to this subspecies but are not sufficient to ameliorate the habitat threats. Therefore, based on the best information available, we have determined that the threats to Trichomanes puctatum ssp. floridanum from habitat destruction, modification, or curtailment are occurring throughout the entire range of the species and are expected to continue into the future.

Factor B. Overutilization for Commercial, Recreational, Scientific, or Educational Purposes

The best available data do not indicate that overutilization for commercial, recreational, scientific, or educational purposes is a threat to Trichomanes punctatum ssp. floridanum.

Factor C. Disease or Predation

No diseases or incidences of predation have been reported for Trichomanes punctatum ssp. floridanum. Therefore, the best available data do not indicate that disease or predation is a threat to the subspecies.

Factor D. The Inadequacy of Existing Regulatory Mechanisms

Under this factor, we examine whether threats to the subspecies discussed under the other factors are continuing due to an inadequacy of an existing regulatory mechanism. Section 4(b)(1)(A) of the Act requires the Service to take into account “those efforts, if any, being made by any State or foreign nation, or any political subdivision of a State or foreign nation, to protect such species. . . .” In relation to Factor D under the Act, we interpret this language to require the Service to consider relevant Federal, State, and tribal laws, regulations, and other such mechanisms that may minimize any of the threats we describe in threat analyses under the other four factors, or otherwise enhance conservation of the species. We give strongest weight to statutes and their implementing regulations and to management direction that stems from those laws and regulations. An example would be State governmental actions enforced under a State statute or constitution or Federal action under statute.

Having evaluated the impact of the threats as mitigated by any such conservation efforts, we analyze under Factor D the extent to which existing regulatory mechanisms are inadequate to address the specific threats to the species. Regulatory mechanisms, if they exist, may reduce or eliminate the impacts from one or more identified threats. In this section, we review existing Federal, State, and local regulatory mechanisms to determine whether they effectively reduce or remove threats to Trichomanes punctatum ssp. floridanum.

Federal

The only known extant populations of Trichomanes punctatum ssp. floridanum occur on State- or County-owned properties and development of these areas will likely require no Federal permit or other authorization. Therefore, projects that affect T. p. ssp. floridanum on State- and County-owned lands do not have a Federal oversight, such as complying with the National Environmental Policy Act (NEPA) (42 U.S.C. 4321 et seq.), unless the project has a Federal nexus (Federal funding, permits, or other authorizations). Therefore, T. p. ssp. floridanum has no direct Federal regulatory protection in its known occupied habitats.

State

FNAI considers the State status of Trichomanes punctatum ssp. floridanum to be S1, “critically imperiled in Florida because of extreme rarity (five or fewer occurrences or less than 1,000 individuals) or because of extreme vulnerability to extinction due to some natural or man-made factor” (FNAI 2013, http://fnai.org/​PDF/​Element_​tracking_​summary_​current.pdf). The IRC considers its status as “critically imperiled” (Gann et al. 2002, pp. 552-554).

The Florida Department of Agriculture and Consumer Services (FDACS) has listed Trichomanes punctatum ssp. floridanum on the Regulated Plant Index (Index) as endangered under Chapter 5B-40, Florida Administrative Code (State of Florida 2013, Florida Statutes: https://www.flrules.org/​gateway/​RuleNo.asp?​title=​PRESERVATION%20OF%20NATIVE%20FLORA%20OF%20FLORIDA&​ID=​5B-40.0055). This listing provides little or no habitat protection beyond the State's Development of Regional Impact process, which discloses impacts from projects, but provides no regulatory protection for State-listed plants on private lands. Florida Statutes 581.185 sections (3)(a) and (b) prohibit any person from willfully destroying or harvesting any species listed as endangered or threatened on the Index, or growing such a plant on the private land of another, or on any public land, without first obtaining the written permission of the landowner and a permit from the Florida Department of Plant Industry. The statute further provides that any person willfully destroying or harvesting; transporting, carrying, or conveying on any public road or highway; or selling or offering for sale any plant listed in the Index as endangered must have a permit from the State at all times when engaged in any such activities. Further, section (10) of the statute provides for consultation similar to section 7 of the Act for listed species, by requiring the Department of Transportation to notify the FDACS and the Endangered Plant Advisory Council of planned highway construction at the time bids are first advertised, to facilitate evaluation of the project for listed plant populations, and to “provide for the appropriate disposal of such plants” (i.e., transplanting).

However, this statute provides no substantive protection of habitat or protection of potentially suitable habitat at this time. Subsections (8)(a) and (b) of the statute waive State regulation for certain classes of activities for all species on the Index, including the clearing or removal of regulated plants for agricultural, forestry, mining, construction (residential, commercial, or infrastructure), and fire-control activities by a private landowner or his or her agent.

The Florida Forest Service (FFS) is the lead managing agency for State forests, as outlined in the Management Lease from the landowner (Board of Trustees of the Internal Improvement Trust Fund of the State of Florida) with guidance provided in Chapters 253, 259, and 589 of the Florida Statutes (State of Florida, 2013 Florida Statutes, http://www.leg.state.fl.us/​Statutes/​index.cfm?​Mode=​View%20Statutes&​Submenu=​1&​Tab=​statutes). FFS is responsible for the management and supervision of the multiple-use guidelines of Withlacoochee State Forest. For research on State Forest lands, prior approval is required. Research deemed legitimate will be issued a State Forest Use Permit (FDACS-11228) or letter of authorization (The Florida Forest Service 2013, State Forest Handbook). Although there is no imminent threat to Withlacoochee State Forest being modified (e.g., logged), altered (e.g., installation of pipelines), or sold for development, the State may be allowed to proceed with such actions only after they have been reviewed and approved at public meetings by the Acquisition and Restoration Council (ARC) and, depending upon the issue, by the Board of Trustees of the Internal Improvement Trust Fund of the State of Florida.

Although the MFLs established by the South Florida Water Management District (SFWMD) in southeast Florida (a separate entity than the Southwest Florida Water Management District (SWFWMD) described earlier) are not directly applicable in the area of Miami Rock Ridge where Trichomanes punctatum ssp. floridanum occurs, they do indirectly limit ground water withdrawals in other areas of south Florida, including other areas of the Miami Rock Ridge. Unfortunately, MFL thresholds in place that establish water withdrawal standards are set so low that protection measures are rarely triggered. These low water level standards may be further exacerbated during times of drought, resulting in even greater impacts to the water table and the overall regional hydrology. Furthermore, MFL standards also do not apply to wells on private property or for consumptive use. The lowering of ground water and associated changes in local ambient humidity have already occurred throughout south Florida and have likely contributed to the decline of T. p. ssp. floridanum and possibly limited distribution and resilience of the subspecies (Grossenbacher 2013, pers. comm.). Plants are likely to be further stressed by the continued lowering of ground water if additional large wells are created on private property for such activities as agriculture or during extended periods of drought because these types of circumstances are not regulated by the water withdrawal standards established by the SFWMD. In general, this regulatory mechanism has not been sufficient to reduce or remove the threat to T. p. ssp. floridanum posed by changes in hydrology discussed under Factor A by ensuring that current water levels will persist into the future.

Sumter County MFLs identified and adopted by the SWFWMD protect the Withlacoochee River and the Tsala Apopka lake chain, which connects to the Withlacoochee in the vicinity of Jumper Creek Tract where Trichomanes punctatum ssp. floridanum occurs. Maintaining designated MFLs will have a direct bearing on the design of future water supply development projects, of which there are several already proposed in Sumter County (Deangelis 2014c, pers. comm.). However, it is uncertain how these future projects would impact extant occurrences of T. p. ssp. floridanum or suitable habitat for the subspecies.

Local

In 1984, section 24-49 of the Code of Miami-Dade County established regulation of County-designated NFCs. These regulations were placed on specific properties throughout the County by an act of the Board of County Commissioners in an effort to protect environmentally sensitive forest lands. The Miami-Dade County Department of Regulatory and Economic Resources (RER) has regulatory authority over these County-designated NFCs and is charged with enforcing regulations that provide partial protection of remaining upland forested areas designated as NFC on the Miami Rock Ridge. NFC regulations are designed to prevent clearing or destruction of native vegetation within preserved areas. Miami-Dade County Code typically allows up to 10 percent of a rockland hammock designated as NFC to be developed for properties greater than 5 acres and requires that the remaining 90 percent be placed under a perpetual covenant for preservation purposes (Joyner 2013a, 2014, pers. comm; Lima 2014, pers. comm.). However, for properties less than 5 acres, up to one-half an acre can be cleared if the request is deemed a reasonable use of property; this allowance oftentimes can be greater than 10 percent of the property (Lima, 2014, pers. comm.). NFC landowners are also required to obtain an NFC permit for any work, including removal of nonnatives within the boundaries of the NFC on their property. When discovered, RER pursues unpermitted work through appropriate enforcement action and seeks restoration when possible. The NFC program is responsible for ensuring that NFC permits are issued in accordance with the limitations and requirements of the county code and that appropriate NFC preserves are established and maintained in conjunction with the issuance of an NFC permit when development occurs.

Although the NFC program is designed to protect rare and important upland (non-wetlands) habitats in south Florida, it is a regulatory strategy with limitations. For example, in certain circumstances where landowners can demonstrate that limiting development to 10 percent does not allow for “reasonable use” of the property, additional development may be approved. Furthermore, Miami-Dade County Code provides for up to 100 percent of the NFC to be developed on a parcel in limited circumstances for parcels less than 2.02 ha (5 ac) in size and only requires coordination with the landowner if they plan to develop property or perform work within the NFC designated area. As such, many of the existing private forested NFC parcels remain fragmented, without management obligations or preserve designation, as development has not been proposed at a level that would trigger the NFC regulatory requirements. Often, nonnative vegetation over time begins to dominate and degrade the undeveloped and unmanaged NFC landscape until it no longer meets the legal threshold of an NFC, which requires the land to be dominated by native vegetation. When development of such degraded NFCs is proposed, Miami-Dade County Code requires delisting of the degraded areas as part of the development process. Property previously designated as NFC is removed from the list even before development is initiated because of the abundance of nonnative species, making it no longer considered to be jurisdictional or subject to the NFC protection requirements of Miami-Dade County Code (Grossenbacher 2013, pers. comm.).

Although Trichomanes punctatum ssp. floridanum is currently afforded some protection from outright destruction on public conservation land, changes in the surrounding landscape that affect the subspecies are not regulated. Any undocumented occurrences of T. p. ssp. floridanum and suitable habitat on private lands are at risk. For example, the private property known as “Monkey Jungle” (historically referred to as Cox Hammock) is a public attraction and is home to a considerable number of primate species. Upon recent visitation to this site (Adimey 2013a, field notes) the habitat features appeared to be similar to other hammocks where T. p. ssp. floridanum currently is known to live (i.e., large solution holes, high humidity, dense canopy, standing water). Although much of the hammock has been altered to accommodate captive animals and visitors, there is still a significant portion of the hammock that remains untouched and overgrown with extensive nonnative, invasive plant species. “Monkey Jungle” receives limited protection under the Miami-Dade County Environmental Protection Ordinance as an NFC, where only portions of NFCs can be cleared once a permit is obtained from the County. The landowner could apply for a permit and destroy undocumented populations of T. p. ssp. floridanum and the subspecies' habitat on this site. Because the site is private and not managed as a preserve (i.e., it is not controlled for nonnative, invasive plant species), degradation of potential habitat for T. p. ssp. floridanum is likely. Furthermore, a change in ownership, accompanied by subsequent modifications in land-use, may cause extirpation of any undocumented T. p. ssp. floridanum populations or negatively impact suitable habitat. Additionally, Miami-Dade County has oversight of any work or research completed within the local preserve areas; permits are required for any outside work or research on County-owned lands in order to further protect the habitat from potential direct or indirect impacts (Gil 2013a, pers. comm.).

Because a comprehensive survey in Sumter County has not yet been conducted, there is a chance of finding new populations of Trichomanes punctatum ssp. floridanum in the area. Any undocumented occurrences and suitable habitat that could be important for reintroduction or recolonization of this subspecies in Sumter County, especially on private lands, are potentially at risk due to development. Under section 13-644(a)(1) of the County code, “[m]ajor developments shall identify and protect habitats of protected wildlife and vegetation species,” and in section 13-644(a)(1)2.b.2, “[n]o permit will be issued for development which results in unmitigated destruction of specimens of endangered, threatened or rare species.” Therefore, County code prevents unmitigated destruction of endangered, threatened, or rare species only when associated with “major developments.” However, these sections do not prevent land destruction or development on private land where any undocumented populations of T. p. ssp. floridanum or suitable habitat for future reintroduction are vulnerable. Current zoning in the Wahoo area limits development to one unit per 4 ha (10 ac); therefore, “major developments” do not seem to be likely in that area. In general, existing county ordinances do not prevent the conversion of habitat to agricultural use or building on sites with endangered, threatened, or rare plant species. Without complete survey information for Sumter County, it is difficult to assess the extent to which unknown occurrences and suitable habitat on private lands are at risk. Agriculture and development are ongoing and promoted in this County, and no regulatory mechanisms exist that protect T. p. ssp. floridanum and its habitat on private lands.

Summary of Factor D

Currently, Trichomanes punctatum ssp. floridanum is found only on State and County lands; however, there is no regulatory mechanism in place that provides substantive protection of habitat or protection of potentially suitable habitat at this time. In addition, subsections of applicable statutes waive State regulation for private landowners or their agents, allowing certain activities to clear or remove species on the Index. Little, if any, protection is afforded to T. p. ssp. floridanum by the established MFLs in south Florida as they are set very low, are rarely triggered, and are not applicable in the portion of the Miami Rock Ridge where the subspecies currently lives. Established MFLs in Sumter County can positively impact areas where T. p. ssp. floridanum occurs, provided that these designated MFLs are maintained when future water supply development projects are undertaken. The NFC program in Miami is designed to protect rare and important upland (non-wetlands) habitats in south Florida; however, this regulatory strategy has several limitations that can negatively affect T. p. ssp. floridanum. Sumter County code prevents unmitigated destruction of endangered, threatened, or rare species only when associated with “major developments” and does not prevent conversion of habitat to agricultural use or building on private property.

Although all extant populations of Trichomanes punctatum ssp. floridanum are afforded some level of protection because they are on public conservation lands, existing regulatory mechanisms have not led to a reduction or removal of threats posed to the subspecies by a wide array of sources (see discussions under Factors A and E).

Factor E. Other Natural or Manmade Factors Affecting Its Continued Existence

Other natural or manmade factors affect Trichomanes punctatum ssp. floridanum to varying degrees. Specific threats include the spread of nonnative, invasive species; potentially incompatible management practices (e.g., inadvertent spraying of T. p. ssp. floridanum while controlling for nonnatives); direct impacts to plants from recreation and other human activities; small population size and isolation; climate change; and the related risks from environmental stochasticity (extreme weather). Each of these threats and its specific effect on T. p. ssp. floridanum are discussed in detail below.

Nonnative Species

Nonnative species can stress, alter, or even destroy native species and their habitats. The threat of nonnative plant species is ongoing due to their: (1) Number and extent, (2) ability to out-compete native species, (3) abundant seed sources, and (4) extensive disturbance within habitats. Further challenges exist due to limitation of resources to combat this threat, as well as the difficulty in managing fragmented hammocks bordered by urban development, which often can serve as seed sources for nonnative species (Bradley and Gann 1999, p. 13). Nonnative, invasive plants compete with native plants for space, light, water, and nutrients, and they limit growth and abundance of natural vegetation and can make habitat conditions unsuitable for native plants.

In south Florida, at least 162 nonnative plant species are known to invade rockland hammocks; impacts are particularly severe on the Miami Rock Ridge (Service 1999, pp. 3-135). Nonnative plant species have significantly affected rockland hammock and mesic hammock habitats where Trichomanes punctatum ssp. floridanum occurs and are considered one of the threats with greatest impact to the subspecies (Snyder et al. 1990, p. 273; Gann et al. 2002, pp. 552-554; FNAI 2010, pp. 22, 26). Nonnative plants outcompete and displace T. p. ssp. floridanum in solution holes, promoting overshading and forming dense strata (layers) in hammocks, which alter the habitat and its surrounding conditions (Possley 2013f, pers. comm.). It has also been suggested that the insular nature of south Florida, as well as the hammocks themselves, predispose this habitat to invasion by nonnative plants (e.g., the proximity of seed sources, which increases the volume of nonnatives and accelerates the time it takes for the arrival and establishment of nonnatives) (Horvitz et al. 1998, p. 961). In many Miami-Dade County parks, nonnative plant species comprise 50 percent of the flora in hammock fragments (Service 1999, pp. 3-135). Horvitz (et al. 1998, p. 968) suggests the displacement of native species by nonnative species in conservation and preserve areas is a complex problem with serious impacts to biodiversity conservation, as management in these areas generally does not protect native species and ecological processes, as intended. Problematic nonnative invasive plants in Miami-Dade County associated with Trichomanes punctatum ssp. floridanum include Schinus terebinthifolius (Brazilian pepper), Bischofia javanica (bishop wood), Syngonium podophyllum (American evergreen), Jasminum fluminense (Brazilian jasmine), Rubus niveus (mysore raspberry), Thelypteris opulenta (jeweled maiden fern), Nephrolepis multiflora (Asian swordfern), Schefflera actinophylla (octopus tree), Jasminum dichotomum (Gold Coast jasmine), Epipremnum pinnatum (centipede tongavine), and Nephrolepis cordifolia (narrow swordfern) (Possley 2013h-i, pers. comm.).

In Sumter County, the most problematic nonnative invasive species occurring in Trichomanes punctatum ssp. floridanum habitat are Tradescantia fluminensis (small leaf spiderwort), and Paederia foetida (skunkvine) (Werner 2014, pers. comm.). Furthermore, Citrus aurantium (bitter orange) is found in this locale and is considered problematic due to its tendency to attract feral hogs, another nonnative species associated with extensive habitat destruction (see below). Agricultural fields in proximity to the Sumter metapopulation are a nonnative seed source, increasing potential encroachment of nonnative plants to the area (Werner 2013b-c, pers. comm.).

In some instances, management of nonnative vegetation may also be detrimental, in that nonnative species may actually provide the necessary canopy to limit sunlight exposure and control humidity and removing the nonnative species exposes the fern. In the case of Castellow Hammock, the majority of the shade near two of the large solution holes containing Trichomanes punctatum ssp. floridanum is provided by giant Schinus terebinthifolius trees; eliminating these trees could likely result in detrimental effects to T. p. ssp. floridanum residing in the underlying solution holes. In hammocks such as Castellow, desiccation from excessive sun exposure due to the removal of S. terebinthifolius canopy has already occurred. In this case, the subpopulation of T. p. ssp. floridanum below where the S. terebinthifolius tree was turned brown; however, T. p. ssp. floridanum could eventually revitalize if sufficient canopy is re-established to limit sunlight exposure (Possley 2013e, pers. comm.). Additionally, nonnative plant control may also become a threat when T. p. ssp. floridanum are inadvertently sprayed while conducting local nonnative removal efforts (Possley 2013e, pers. comm.).

Nonnative plant species are also a concern on private lands, where often these species are not controlled due to associated costs, lack of interest, or lack of knowledge of detrimental impacts to the ecosystem. Undiscovered populations of Trichomanes punctatum ssp. floridanum on private lands could certainly be at risk. Overall, active management is necessary to control for nonnative species and to protect unique and rare habitat where T. p. ssp. floridanum occurs (Snyder et al. 1990, p. 273). Treatment of nonnative plant species should consider canopy and humidity needs of T. p. ssp. floridanum.

Nonnative feral hogs living in the Withlacoochee State Forest are also considered a threat to this plant. Surveys in Sumter County have revealed evidence of hogs laying against or rubbing their bodies against large rocks, removing existing vegetation in the process. Recently, van der Heiden and Johnson (2013, p. 11) found one small rock where Trichomanes punctatum ssp. floridanum had been scraped off when a hog rubbed itself on the rock after wallowing in the mud. Furthermore, rooting from hogs can destroy existing habitat by displacing smaller rocks where T. p. ssp. floridanum is found to grow and potentially damaging or eliminating a cluster (Werner 2013d, pers. comm.). In Withlacoochee State Forest, damaged areas from feral hogs are also more susceptible to invasion from nonnative plant species, such as Urena lobata (Caesarweed) and Tradescantia fluminensis (small-leaf spiderwort) (Werner 2013a, pers. comm.). If feral hogs continue to forage in areas where T. p. ssp. floridanum lives, it is possible entire clusters inhabiting one rock/boulder could be eliminated.

In recent years, scientists in south Florida have noticed an increase in sightings of the nonnative genus Liguus (Cuban tree snails). Although snail grazing has not been observed on Trichomanes punctatum ssp. floridanum, it has been documented on other rare ferns living in the same habitat and could possibly be a threat in the future, either by this snail or another introduced species (Possley 2013b, c, pers. comm.).

Climate Change

Climatic changes, including sea level rise (SLR), are occurring in the State of Florida and are impacting associated plants, animals, and habitats. The term “climate,” as defined by the Intergovernmental Panel on Climate Change (IPCC), refers to the mean and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (IPCC 2013, p. 1450). The term “climate change” thus refers to a change in the mean or variability of one or more measures of climate (e.g., temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is due to natural variability, human activity, or both (IPCC 2013, p. 1450). A recent compilation of climate change and its effects is available from reports of the Intergovernmental Panel on Climate Change (IPCC) (IPCC 2013, entire).

Various changes in climate may have direct or indirect effects on species. These effects may be positive, neutral, or negative, and they may change over time, depending on the species and other relevant considerations, such as interactions of climate with other variables (e.g., habitat fragmentation) (IPCC 2007, pp. 8-14, 18-19). Projected changes in climate and related impacts can vary substantially across and within different regions of the world (e.g., IPCC 2007, pp. 8-12). Therefore, we use “downscaled” projections when they are available and have been developed through appropriate scientific procedures (see Glick et al. 2011, pp. 58-61, for a discussion of downscaling). As to Trichomanes punctatum ssp. floridanum, downscaled projections suggest that SLR is the largest climate-driven challenge to low-lying coastal areas in the subtropical ecoregion of southern Florida (U.S. Climate Change Science Program (USCCSP) 2008, pp. 5-31, 5-32). All Miami-Dade County populations of T. p. ssp. floridanum occur at elevations 2.83-4.14 m (9.29-13.57 ft) above sea level, making the subspecies highly susceptible to increased storm surges and related impacts associated with SLR, whereas the Sumter County populations are at approximately 10.40 m (34.12 ft) above sea level and significantly farther from the coast.

The long-term record at Key West shows that sea level rose on average 0.229 cm (0.090 in) annually between 1913 and 2013 (National Oceanographic and Atmospheric Administration (NOAA) 2013, p. 1). This equates to approximately 22.9 cm (9.02 in) over the last 100 years. IPCC (2008, p. 28) emphasized it is very likely that the average rate of SLR during the 21st century will exceed the historical rate. The IPCC Special Report on Emission Scenarios (2000, entire) presented a range of scenarios based on the computed amount of change in the climate system due to various potential amounts of anthropogenic greenhouse gases and aerosols in 2100. Each scenario describes a future world with varying levels of atmospheric pollution leading to corresponding levels of global warming and corresponding levels of SLR. The IPCC Synthesis Report (2007, entire) provided an integrated view of climate change and presented updated projections of future climate change and related impacts under different scenarios.

Subsequent to the 2007 IPCC Report, the scientific community has continued to model SLR. Recent peer-reviewed publications indicate a movement toward increased acceleration of SLR. Observed SLR rates are already trending along the higher end of the 2007 IPCC estimates, and it is now widely held that SLR will exceed the levels projected by the IPCC (Rahmstorf et al. 2012, p. 1; Grinsted et al. 2010, p. 470). Taken together, these studies support the use of higher end estimates now prevalent in the scientific literature. Recent studies have estimated global mean SLR of 1.0-2.0 m (3.3-6.6 ft) by 2100 as follows: 0.75-1.90 m (2.50-6.20 ft; Vermeer and Rahmstorf 2009, p. 21530), 0.8-2.0 m (2.6-6.6 ft; Pfeffer et al. 2008, p. 1342), 0.9-1.3 m (3.0-4.3 ft; Grinsted et al. 2010, pp. 469-470), 0.6-1.6 m (2.0-5.2 ft; Jevrejeva et al. 2010, p. 4), and 0.5-1.4 m (1.6-4.6 ft; National Research Council 2012, p. 2).

Other processes expected to be affected by projected warming include temperatures, rainfall (amount, seasonal timing, and distribution), and storms (frequency and intensity) (see “Environmental Stochasticity”, below). Models where sea level temperatures are increasing also show a higher probability of more intense storms (Maschinski et al. 2011, p. 148). The Massachusetts Institute of Technology (MIT) modeled several scenarios combining various levels of SLR, temperature change, and precipitation differences with human population growth, policy assumptions, and conservation funding changes (see “Alternative Future Landscape Models”, below). All of the scenarios, from small climate change shifts to major changes, indicate significant effects on coastal Miami-Dade County. The Science and Technology Committee of the Miami-Dade County Climate Change Task Force (Wanless et al. 2008, p. 1) recognizes that significant SLR is a serious concern for Miami-Dade County in the near future. In a January 2008 statement, the committee warned that sea level is expected to rise at least 0.9-1.5 m (3.0-5.0 ft) within this century (Wanless et al. 2008, p. 3). With a 0.9-1.2 m (3.0-4.0 ft) rise in sea level (above baseline) in Miami-Dade County, spring high tides would be at about 1.83-2.13 m (6.0-7.0 ft); freshwater resources would be gone; the Everglades would be inundated on the west side of Miami-Dade County; the barrier islands would be largely inundated; storm surges would be devastating to coastal habitat and associated species; and landfill sites would be exposed to erosion, contaminating marine and coastal environments. Freshwater and coastal mangrove wetlands will be unable to keep up with or offset SLR of 0.61 m (2.0 ft) per century or greater. With a 1.52 m (5.0 ft) rise, Miami-Dade County will be extremely diminished (Wanless et al. 2008, pp. 3-4).

Prior to inundations from SLR, there will likely be habitat transitions related to climate change, including changes to hydrology and increasing vulnerability to storm surge. Hydrology has a strong influence on plant distribution in coastal areas (IPCC 2008, p. 57). Such communities typically grade from salt to brackish to freshwater species. From the 1930s to 1950s, increased salinity of coastal waters contributed to the decline of cabbage palm forests in southwest Florida (Williams et al. 1999, pp. 2056-2059), expansion of mangroves into adjacent marshes in the Everglades (Ross et al. 2000, pp. 101, 111), and loss of pine rockland in the Keys (Ross et al. 1994, pp. 144, 151-155). In Florida, pine rocklands transition into rockland hammocks, and, as such, these habitat types are closely associated in the landscape. A study conducted in one pine rockland location in the Florida Keys (with an average elevation of 0.89 m (2.90 ft)) found an approximately 65 percent reduction in an area occupied by South Florida slash pine over a 70-year period, with pine mortality and subsequent increased proportions of halophytic (salt-loving) plants occurring earlier at the lower elevations (Ross et al. 1994, pp. 149-152). During this same time span, local sea level had risen by 15 cm (6 in), and Ross et al. (1994, p. 152) found evidence of groundwater and soil water salinization. Extrapolating this situation to hardwood hammocks is not straightforward, but it suggests that changes in rockland hammock species composition may not be an issue in the immediate future (5-10 years); however, over the long term (within the next 10-50 years), it may be an issue if current projections of SLR occur and freshwater inputs are not sufficient to maintain high humidities and prevent changes in existing canopy species through salinization (Saha et al. 2011, pp. 22-25). Ross et al. (2009, pp. 471-478) suggested that interactions between SLR and pulse disturbances (e.g., storm surges) can cause vegetation to change sooner than projected based on sea level alone. Patterns of human development will also likely be significant factors influencing whether natural communities can move and persist (IPCC 2008, p. 57; USCCSP 2008, p. 7-6).

Impacts from climate change including regional SLR have been studied for coastal hammocks but not rockland hammock habitat. Saha (et al. 2011, pp. 24-25) conducted a risk assessment on rare plant species in ENP and found that impacts from SLR have significant effects on imperiled taxa. This study also predicted a decline in the extent of coastal hammocks with initial SLR, coupled with a reduction in freshwater recharge volume and an increase in pore water (water filling spaces between grains of sediment) salinity, which will push hardwood species to the edge of their drought (freshwater shortage and physiological) tolerance, jeopardizing critically imperiled and/or endemic species with possible extirpation. In south Florida, SLR of 1-2 m (0.30-0.61 ft) is estimated by 2100, which is on the higher end of global estimates for SLR. These projected increases in sea level pose a threat to coastal plant communities and habitats from mangroves at sea level to salinity-intolerant, coastal rockland hammocks where elevations are generally less than 2.00 m (6.1 ft) above sea level (Saha et al. 2011, p. 2). Loss or degradation of these habitats can be a direct result of SLR or in combination of several other factors, including diversion of freshwater flow, hurricanes, and exotic plant species infestations, which can ultimately pose a threat to rare plant populations (Saha et al. 2011, p. 24).

Saha (et al. 2011, p. 4) suggested that the rising water table accompanying SLR will shrink the vadose zone (the area which extends from the top of the ground surface to the water table); increase salinity in the bottom portion of the freshwater lens, thereby increasing brackishness of plant-available water; and influence tree species composition of coastal hardwood hammocks based upon species-level tolerance to salinity and/or drought. Evidence of population declines and shifts in rare plant communities, along with multi-trophic effects, already have been documented on the low-elevation islands of the Florida Keys (Maschinski et al. 2011, p. 148). Altered freshwater inputs can lead to the disappearance or decline of critically imperiled coastal plant species such as Trichomanes punctatum ssp. floridanum. Shifts in freshwater flows, annual precipitation, and variability in SLR can impact salinity regimes. Although it is unknown if salinity changes will impact existing habitat where T. p. ssp. floridanum currently lives, it should be noted that salinity-intolerant plants can become stressed within a few weeks from exposure to saline conditions, and persistent conditions can promote colonization by more salinity-tolerant species, thereby leading to an irreversible composition change even if the salinity is lower over subsequent years (Saha et al. 2011, p. 23).

In some areas of south Florida, precipitation is the main source of fresh water. Predictive climate change models demonstrate periods of drought will pose a threat to existing populations of Trichomanes punctatum ssp. floridanum. Saha (et al. 2011, pp. 19-21) found that during times of drought and resultant salinity stress, coastal hardwood tree density from the canopy was lost, while other species showed an increase. Areas with a deeper freshwater lens, such as rockland hammocks, may be able to sustain vegetation during periods of drought; however, this is currently unknown. Some tree species in coastal hammocks have the ability to access pockets of fresh water and tolerate mild salinities. These initial responses to salinity increases may trigger responses similar to drought, while prolonged exposure may cause irreversible toxicity caused by accumulation of salts (Munns 2002, p. 248), causing a reduction in canopy or mortality (Maschinski et al. 2009, entire paper). Impacts from climate change causing shifts in local plant communities and invasion of additional nonnative plant species may be lessened by the ability of hardwood hammocks (such as rockland hammocks) to harvest rainfall water and retain it in the highly organic soil and lower their transpiration (i.e., the process of water movement through a plant and its evaporation from leaves and stems) during the dry season (Saha et al. 2011, p. 24).

Drier conditions and increased variability in precipitation associated with climate change are expected to hamper successful regeneration of forests and cause shifts in vegetation types through time (Wear and Greis 2012, p. 39). With regard to Trichomanes punctatum ssp. floridanum, any weather shifts causing less precipitation would likely impact the viability of existing populations and could potentially limit future reproduction if droughts were to become a common occurrence. Ecosystem shifts would result in rockland and mesic hammocks having drier conditions; regular droughts; and changes in humidity, temperature and canopy. Increases in the scale, frequency, or severity of droughts and wildfires (see “Fires” section, below) could have negative effects on this taxon considering its general vulnerability due to small population size, restricted range, few populations, and relative isolation.

Climate change impacts specifically for Trichomanes punctatum ssp. floridanum may be numerous and vary depending on factors such as severity, the speed at which climate changes occur, timing, health of the species, and habitat and tolerance of species. Overall, healthy ecosystems can support greater biodiversity, which is considered one of the best strategies to combat impacts of climate change. Removing nonnative plants and minimizing natural disturbance impacts and other exogenous stresses can improve resiliency to climate change impacts (Maschinski et al. 2011, p. 159). In general, the best ways to prepare and protect rare species, such as T. p. ssp. floridanum, from impacts of climate change include actively managing habitats to improve resilience, population growth, and potential for natural dispersal, and controlling for nonnative species. Efforts to actively manage for resilience are currently limited for both metapopulations of T. p. ssp. floridanum due to logistic feasibility, insufficient funding and research, small and fragmented existing populations, and lack of successful reintroduction efforts into the wild.

Alternative Future Landscape Models

To accommodate the large uncertainty in SLR projections, researchers must estimate effects from a range of scenarios. Various model scenarios developed at MIT and GeoAdaptive Inc. have projected possible trajectories of future transformation of the peninsular Florida landscape by 2060 based upon four main drivers: climate change, shifts in planning approaches and regulations, human population change, and variations in financial resources for conservation (Vargas-Moreno and Flaxman 2010, pp. 1-6). The scenarios do not account for temperature, precipitation, or species habitat shifts due to climate change, and no storm surge effects are considered. The current MIT scenarios in Florida range from an increase of 0.09-1.0 m (0.3-3.3 ft) by 2060.

Based on the most recent estimates of SLR and the best available data at this time, we evaluated potential effects of SLR using the current “worst case” (e.g., the highest range for SLR) MIT scenario as well as comparing elevations of remaining rockland hammock fragments in Miami-Dade County and mesic hammocks in Sumter County with extant populations of Trichomanes punctatum ssp. floridanum. The “worst case” MIT scenario assumes SLR of 1.0 m (3.3 ft) by 2060, low financial resources, a “business as usual” approach to planning, and a doubling of human population.

Based on the 1.0-m (3.3-ft) scenario, none of the rockland hammocks in Miami-Dade County where extant populations of Trichomanes punctatum ssp. floridanum occur would be inundated. However, all four populations would be within 9.66 km (6.0 mi) of saltwater, increasing the likelihood of localized vegetation shifts within the rockland hammocks and vulnerability to natural stochastic events such as hurricanes and tropical storms. The 1.0-m SLR scenario shows existing rockland hammocks in Miami-Dade County (that do not contain T. p. ssp. floridanum) directly adjacent to saltwater. Although these existing hammocks are located in higher elevation areas along the coastal ridge, changes in the salinity of the water table and soils, along with additional vegetation shifts in the region, are likely. A few remaining rockland hammocks further inland (e.g., Big and Little George Hammocks) are located in highly urbanized areas; these hammocks are small and fragmented, reducing the chances of further development due to SLR in the area. Actual impacts may be greater or less than anticipated based upon the high variability of factors involved (e.g., SLR, human population growth) and the assumptions made in this model.

A projected SLR (using elevation data) of 2.0 m (6.6 ft) appears to inundate much larger portions of urban Miami-Dade County. This evaluation was not based on any modeling, as opposed to the previous 1.0-m scenario; rather, this scenario examines current elevation based on LiDAR data. Under this 2.0-m (6.6-ft) SLR scenario, none of the four hammocks where Trichomanes punctatum ssp. floridanum is known to occur will be inundated, but all will be within approximately 2.41 km (1.5 mi) of saltwater in the inundated transverse glades joining the enlarged Biscayne Bay. Castellow Hammock will be the least impacted at approximately 2.41 km (1.5 mi) from saltwater, while Hattie Bauer will be adjacent to saltwater. Fuchs and Meissner hammocks will be 1.61 km (1.0 mi) from saltwater and will be surrounded by more wetlands. This scenario will leave all these locations extremely vulnerable to vegetation shifts, natural stochastic events, and loss of existing habitat and land protection. Of the remaining rockland hammocks not containing T. p. ssp. floridanum in south Florida, most would be fully or partially inundated after a 2.0-m (6.6-ft) SLR, except for the hammocks located on the higher elevated coastal ridge, which would still be adjacent to saltwater.

Due to the higher elevation and inland location of Sumter County in north Florida, existing populations of Trichomanes punctatum ssp. floridanum and associated habitat will not be impacted by 1.0- and 2.0-m (3.3- and 6.6-ft) rises in sea level. The 2.0-m (6.6-ft) SLR scenario would still leave the Sumter occurrences approximately 37.0 km (23.0 mi) from saltwater. Regional shifts in water table salinity, soils, or vegetation are not expected.

Environmental Stochasticity

Endemic species whose populations exhibit a high degree of isolation, such as Trichomanes punctatum ssp. floridanum, are extremely susceptible to extinction from both random and nonrandom catastrophic natural or human-caused events. Small populations of species, without positive growth rates, are considered to have a high extinction risk from site-specific demographic and environmental stochasticity (Lande 1993, pp. 911-927). Populations at the edge of a species' range, as may be the case with T. p. ssp. floridanum in Sumter County, may be particularly vulnerable to environmental stochasticity, as they may also be at the edge of their physiological and adaptive limits (Baguette 2004, p. 216).

The climate in Florida is driven by a combination of local, regional, and global events, regimes, and oscillations (e.g., El Niño Southern Oscillation with a frequency of every 4 to 7 years, solar cycle every 11 years, and the Atlantic Multi-decadal Oscillation); however, the exact magnitude, direction, and distribution of these climatic influences on a regional level are difficult to project. There are three main “seasons” in Florida: (1) The wet season, which is hot, rainy, and humid from June through October; (2) the official hurricane season that extends one month beyond the wet season (June 1 through November 30), with peak season being August and September; and (3) the dry season, which is drier and cooler, from November through May (Miller 2013, pers. comm.). In the dry season, periodic surges of cool and dry continental air masses influence the weather with short-duration rain events followed by long periods of dry weather.

Florida is considered the most vulnerable State in the United States to hurricanes and tropical storms (Florida Climate Center, http://coaps.fsu.edu/​climate_​center). Based on data gathered from 1856 to 2008, Klotzbach and Gray (2009, p. 28) calculated the climatological probabilities for each State being impacted by a hurricane or major hurricane in all years over the 152-year timespan. Of the coastal States analyzed, Florida had the highest climatological probabilities, with a 51 percent probability of a hurricane (Category 1 or 2) and a 21 percent probability of a major hurricane (Category 3 or higher). From 1856 to 2008, Florida experienced 109 hurricanes and 36 major hurricanes. Given the few isolated populations and restricted range of Trichomanes punctatum ssp. floridanum in locations prone to storm influences (i.e., Miami-Dade County), this subspecies is at substantial risk from hurricanes, storm surges, and other extreme weather events.

Natural stochastic events can pose a threat to the persistence of Trichomanes punctatum ssp. floridanum through the destruction of existing habitat. Some climate change models predict increased frequency and duration of severe storms, including hurricanes and tropical storms (McLaughlin et al. 2002, p. 6074; Cook et al. 2004, p. 1015; Golladay et al. 2004, p. 504). Other models predict hurricane and tropical storm frequencies in the Atlantic are expected to decrease between 10-30 percent by 2100 (Knutson et al. 2008, pp. 1-21). For those models that predict fewer hurricanes, predictions of hurricane wind speeds are expected to increase by 5-10 percent due to an increase in available energy for intense storms. Increases in hurricane winds can elevate the chances of damage to existing canopy.

In south Florida, tropical hardwood hammocks forests are known to experience frequent disturbances from hurricanes (Horvitz et al. 1998, p. 947). Hurricanes and tropical storms can damage existing canopy, which provides shade and cover from wind; canopy loss of any kind is believed to be the threat with greatest impact to existing metapopulations of Trichomanes punctatum ssp. floridanum (Adimey 2013b, field notes; Possley 2013p, pers. comm.). For example, impacts from Hurricane Andrew in 1992 were thought to be responsible for the temporary loss of this subspecies from Hattie Bauer Hammock, where it had been observed for many years. Following this hurricane, the canopy was destroyed, allowing increased exposure to sunlight for several years. T. p. ssp. floridanum was not seen again in Hattie Bauer Hammock until 2011 (Possley 2013p, pers. comm.). Destruction of habitat due to hurricanes has also been documented in Sumter County in the Indian Ledges Hammock located near the town of Wahoo. This hammock, known to host a variety of rare ferns, orchids, and large trees, sustained severe damage from several hurricanes in 2004; very few original plant species once found in Indian Ledges Hammock exist in this location today (Deangelis 2014a, pers. comm.).

Historically, Trichomanes punctatum ssp. floridanum may have benefitted from more abundant and contiguous habitat to buffer it from storm events. The destruction and modification of native habitat, combined with small population size, has likely contributed over time to the stress, decline, and, in some instances, extirpation of populations or local occurrences due to stochastic events.

A study conducted by Horvitz et al. (1998, p. 947) found that the regeneration of forest species after stochastic events depended on the amount of canopy disturbance, the time since disturbance, and the biological relationship between the individual species and its environment. Following Hurricane Andrew, the relative abundance and life-stage changed for many nonnative plant species within Miami-Dade County. These shifts continued to occur as a result of subsequent stochastic events, suggesting hurricanes can alter long-term hammock structure and the ongoing changes in species composition (Horvitz et al. 1998, pp. 961, 966).

Stochastic events resulting in changes in normal precipitation (amount, seasonal timing, and distribution) and extreme temperature fluctuations may also impact Trichomanes punctatum ssp. floridanum. During the winter dry season, T. p. ssp. floridanum can become desiccated without periodic rainfall and then recover during the wet season. Multi-year droughts may negatively impact populations. While droughts are natural events, they are a threat because there are so few populations of this subspecies. Specific range requirements regarding humidity, temperature, and precipitation are not known at this time for T. p. ssp. floridanum, making it difficult to accurately determine what impacts will occur from modifications in current environmental conditions where extant metapopulations occur. Extreme temperature changes such as cold events in south Florida or freezing temperatures in central Florida could have devastating impacts on this subspecies. The small size of each population makes this plant especially vulnerable, in which the loss of even a few individuals could reduce the viability of a single population.

Due to the small size of existing populations of Trichomanes punctatum ssp. floridanum, its genetic variability and overall resilience is likely low. These factors, combined with additional stress from habitat modifications (e.g., hydrological changes) may increase the inherent risk of stochastic events that impact this subspecies (Matthies et al. 2004, pp. 481-488). Additionally, stochastic events are expected to exacerbate the impacts of regional drainage and subsequent drops in humidity. For these reasons, T. p. ssp. floridanum is at risk of extirpation during extreme stochastic events. We have determined that these natural stochastic events as addressed above are a threat to the persistence of this subspecies in the future (Adimey 2013b, field notes; Possley 2013p, pers. comm.).

Fires

Although fires are not a current concern for existing populations of Trichomanes punctatum ssp. floridanum, they have been known to impact populations in the past. Craighead (1963, p. 39) noted that extensive fires in hammocks eliminated ferns in much of their former range. Drainage efforts in the early 1900s also influenced the occurrence of fire; Phillips (1940, p. 166) noted that the frequent occurrence of fires in the late 1930s in southern Florida resulted in widespread destruction of flora. Fires may have been a factor in the disappearance of this taxon in Royal Palm Hammock, which suffered multiple fires in the first half of the 1900s according to photographs from J.K. Small (1916, http://www.floridamemory.com/​items/​show/​49132;​; 1917, http://www.floridamemory.com/​items/​show/​49465). In recent decades, wildfires have been controlled in most rockland hammocks due to the extensive urbanization in Miami-Dade County. However, fires do have the potential to impact T. p. ssp. floridanum during periods of prolonged drought. While fires are a natural component of some ecosystems in south Florida, fires in hammocks can set back succession to pine rockland or other communities and will directly kill many plant species that are not adapted to fires.

Generally, hammock environments are considered less susceptible to wildfires because their shaded, humid microclimate is not conducive to fire spread (Snyder et al. 1990, p. 258). Additionally, rockland hammocks occupy elevated, rarely inundated, and fire-free sites in all three of the major rockland areas in south Florida (Snyder et al. 1990, p 239). Mesic hammocks are also considered fire resistant in that many occur as “islands” on high ground within basin or floodplain wetlands, as patches of oak/palm forest in dry prairie or flatwoods communities, on river levees, or in ecotones between wetlands and upland communities, and possess high moisture soils due to heavy shading of the ground layer and accumulation of litter (FNAI 2010, p. 20). Additionally, wildfires are now considered a minor stressor in mesic hammocks because of the use of prescribed burns (Werner 2013d, pers. comm; Possley 2013l, pers. comm.).

Snyder (et al. 1990, p. 238) points out that the high organic content of hammock soils in south Florida can enable it to burn; however, soil fires typically only burn in hammocks in times of drought or when they are intentionally set (Snyder et al. 1990, pp. 258-260). This stressor is considered minimal in that fires typically will go out when they reach hammock margins, whether entering from pineland or some other community due to the presence of hardwood leaf litter lying directly on moist organic soil with minimal herbaceous fuel.

Although wildfires are known to occur in Miami-Dade and Sumter Counties, they are not currently considered a threat at this time due to regional prescribed burn efforts, the natural fire-resistant features of these two habitats, and, in Sumter County, hydric hammock surrounding Trichomanes punctatum ssp. floridanum populations. However, under future projected climate change scenarios, we expect drought conditions to exacerbate the effects on T. p. ssp. floridanum to a level at which fire becomes a threat in the future.

Public Use/Encroachment

In Miami-Dade County, two of the four hammocks containing Trichomanes punctatum ssp. floridanum (Castellow and Hattie Bauer) are accessible to the public. However, in both cases, T. p. ssp. floridanum is not accessible from the nature trail (Possley 2013h, pers. comm.). If public use were to increase significantly at any of the Miami-Dade hammocks, populations of T. p. ssp. floridanum could become at risk. For example, because the taxon grows along the rim and walls of solution holes, people climbing into these holes could damage existing populations; increased use could also introduce additional nonnative seed sources into the habitat. Similarly, climbing on boulders where the fern occurs in Sumter County could also cause damage. However, due to the low amount of visitation at the Withlacoochee State Forest (Werner 2013b-c, pers. comm.), public use and encroachment does not appear to be occurring at this time, and we have determined it does not pose a threat to T. p. ssp. floridanum.

Small Population Size and Isolation

Low population resilience is a serious concern for species that are restricted to geographically limited areas, as they are inherently more vulnerable to extinction than widespread species due to an increased risk of genetic bottlenecks, random demographic fluctuations, climate change, and localized catastrophes such as hurricanes and disease outbreaks (Mangel and Tier 1994, p. 607; Pimm et al. 1988, p. 757). These problems are further magnified when populations are few, populations are restricted to very small geographic areas, and numbers of individuals are limited, as in the case of Trichomanes punctatum ssp. floridanum. Although robust population viability analyses (including minimum viable population calculations) have not been conducted for this subspecies, indications are that most existing populations are minimal in terms of abundance and size. Lack of dispersal between occurrences is also a stressor that contributes to the low population resilience for this subspecies (see “Habitat Fragmentation” under Factor A).

Limited genetic variability will also impact population resilience. The ability of populations to adapt to environmental change is dependent upon genetic variation, a property of populations that derives from its members possessing different forms (i.e., alleles) of the same gene (Primack 1998, p. 283). High genetic diversity can enhance a species' persistence in a changing environment (Lynch and Lande 1993, pp. 246-247). Although Trichomanes punctatum ssp. floridanum can grow in clusters, separate clusters are not necessarily different individuals, as they may have been connected by one or more stems in the past (Possley 2014b, pers. comm.). Thus, a population of T. p. ssp. floridanum containing many clusters may not have greater genetic diversity than a population with few clusters. Because there are only six extant populations of T. p. ssp. floridanum, with few plants, the genetic variability is considered low, and the subspecies is inherently at risk due to stochastic events and changes in environmental conditions (Matthies et al. 2004, pp. 481-488).

In summary, population resilience is impacted by factors such as small population size, vulnerability to random demographic fluctuations or natural catastrophes, and low genetic diversity, which is further magnified by synergistic (interaction of two or more components) effects with other threats, such as those discussed above. In evaluating the stressor of low population resilience to Trichomanes punctatum ssp. floridanum that could arise due to small population size, we reviewed the limited data available concerning abundance at each of the occurrences across the subspecies' range. This represents a conservative classification of small population size, as available data do not discriminate among individual plants and life-history stages. These small populations are at risk of adverse effects from reduced genetic variation, an increased risk of inbreeding depression, and reduced reproductive output. Many of these populations are small and isolated from each other, decreasing the likelihood that they could be naturally reestablished in the event that extinction from one location would occur.

Conservation Efforts To Reduce Other Natural or Manmade Factors Affecting Its Continued Existence

Miami-Dade County and the State of Florida have ongoing nonnative plant management programs to reduce threats on public lands, as funding and resources allow. In Miami-Dade County, nonnative, invasive plant management is very active, with a goal to treat all publically owned properties at least once a year and more often in many cases. Annual monitoring of Trichomanes punctatum ssp. floridanum is conducted by Fairchild, which records health and size of individual clusters of the subspecies along with potential new stressors, including nonnative, invasive species or habitat destruction; reports are forwarded to the County preserve manager for further attention (Possley 2013p, pers. comm.). IRC also conducts research and monitoring in various hammocks within Miami-Dade County for various rare and endangered plant species; nonnative, invasive species are documented, along with any occurrence of human disturbance (van der Heiden 2013i, pers. comm.). In Sumter County, the Florida Park Service surveys each State-owned property at least once a year to manage for nonnative plants (Werner 2013a-b, pers. comm.). Furthermore, Withlacoochee State Forest conducts prescribed burning on an annual basis, controlling regional wildfires in dry swamps and mesic hammocks.

Continuing efforts to propagate Trichomanes punctatum ssp. floridanum in-vitro may eventually lead to the establishment of healthy populations that can be reintroduced in locations where the taxon once occurred or introduced to new areas deemed appropriate. These efforts can assist with combating potential or realized impacts from natural stochastic events that may harm or destroy existing populations.

Summary of Factor E

Stochastic events resulting in changes in canopy structure and environmental conditions within the taxon's current habitat are considered threats to existing and future populations of T. p. ssp. floridanum. This is especially alarming since droughts, tropical storms, and hurricanes are common occurrences in Florida. Changes associated with these events have the potential to limit reproduction and compromise overall health in the long term, making plants more vulnerable to other stressors (e.g., periodic, long-term droughts, hurricanes) or cause extirpations. As few populations remain, the entire taxon is at risk of extinction during these events. Climatic changes, including SLR, are longer term concerns expected to exacerbate existing impacts and ultimately reduce the extent of available habitat for T. p. ssp. floridanum.

The presence of nonnative species, including other plants and feral hogs, is also a threat, but may be reduced on public lands due to active programs by Miami-Dade County and the State. The majority of the remaining populations of this plant are small and geographically isolated, and genetic variability is likely low, increasing the inherent risk due to overall low resilience of this subspecies. Furthermore, the isolated existence of Trichomanes punctatum ssp. floridanum makes natural recolonization of extirpated populations virtually impossible without human intervention. Although considered stressors, wildfires and public use at extant sites are minimal and do not rise to the level of a threat.

Cumulative Effects of Threats

When two or more threats affect Trichomanes punctatum ssp. floridanum occurrences, the effects of those threats could interact or become compounded, producing a cumulative adverse effect that is greater than the impact of either threat alone. The most obvious cases in which cumulative adverse effects would be significant are those in which small populations (Factor E) are affected by threats that result in destruction or modification of habitat (Factor A). The limited distributions and small population sizes of T. p. ssp. floridanum make it extremely susceptible to the detrimental effects of further habitat modification, degradation, and loss, as well as other anthropogenic threats. Mechanisms leading to the decline of this taxon, as discussed above, range from local (e.g., hydrology changes, agriculture) to regional (e.g., development, fragmentation, nonnative species) to global influences (e.g., climate change, SLR). The synergistic effects of threats, such as impacts from hurricanes on a species with a limited distribution and small populations, make it difficult to predict population viability. While these stressors may act in isolation, it is more probable that many stressors are acting simultaneously (or in combination) on populations of T. p. ssp. floridanum, making this subspecies more vulnerable.

Proposed Determination

Section 4 of the Act (16 U.S.C. 1533), and its implementing regulations at 50 CFR part 424, set forth the procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, we may list a species based on (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) Overutilization for commercial, recreational, scientific, or educational purposes; (C) Disease or predation; (D) The inadequacy of existing regulatory mechanisms; or (E) Other natural or manmade factors affecting its continued existence. Listing actions may be warranted based on any of the above threat factors, singly or in combination.

We have carefully assessed the best scientific and commercial data available regarding the past, present, and future threats to Trichomanes punctatum ssp. floridanum. T. p. ssp. floridanum has been extirpated from the majority of its historical range, and the primary threats of habitat destruction and modification resulting from human population growth and development, agricultural conversion, regional drainage, and resulting changes in canopy and hydrology (Factor A); competition from nonnative, invasive species (Factor E); changes in climatic conditions, including sea level rise (Factor E); and natural stochastic events (Factor E) remain threats for existing populations. Existing regulatory mechanisms have not led to a reduction or removal of threats posed to the subspecies from these factors (see Factor D discussion). These threats are ongoing, rangewide, and expected to continue in the future. Populations of T. p. ssp. floridanum are relatively small and isolated from one another, and their ability to recolonize suitable habitat is unlikely without human intervention. Because of the current condition of the extant populations and life-history traits of the subspecies, it is vulnerable to natural or human-caused changes in its currently occupied habitats. The threats have had and will continue to have substantial adverse effects on T. p. ssp. floridanum and its habitat. Although attempts are ongoing to alleviate or minimize some of these threats at certain locations, all populations appear to be impacted by one or more threats.

The Act defines an endangered species as “any species which is in danger of extinction throughout all or a significant portion of its range” and a threatened species as “any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.” As described in detail above, this plant is currently at risk throughout all of its range due to the immediacy, severity, significance, timing, and scope of those threats. Impacts from these threats are ongoing and increasing; singly or in combination, these threats place the subspecies in danger of extinction. The risk of extinction is high because the populations are small, are isolated, and have limited to no potential for recolonization. Numerous threats are currently ongoing and are likely to continue in the foreseeable future, at a high intensity and across the entire range of this subspecies. Furthermore, natural stochastic events and changes in climatic conditions pose a threat to the persistence of the subspecies, especially in light of the fact these events cannot be controlled and mitigation measures have yet to be addressed. Individually and collectively, all these threats can contribute to the local extirpation and potential extinction of this subspecies. Because these threats are placing this subspecies in danger of extinction throughout its range, we have determined this plant meets the definition of an endangered species. Therefore, on the basis of the best available scientific and commercial information, we propose to list Trichomanes punctatum ssp. floridanum as an endangered species in accordance with sections 3(6) and 4(a)(1) of the Act. We find that a threatened species status is not appropriate for T. p. ssp. floridanum because of the contracted range of the subspecies and because the threats are occurring rangewide, are ongoing, and are expected to continue into the future.

Under the Act and our implementing regulations, a species may warrant listing if it is endangered or threatened throughout all or a significant portion of its range. The threats to the survival of Trichomanes punctatum ssp. floridanum occur throughout the subspecies' range and are not restricted to any particular significant portion of that range. Accordingly, our assessment and proposed determination applies to the subspecies throughout its entire range.

Significant Portion of the Range

Because we have determined that Trichomanes punctatum ssp. floridanum is an endangered species throughout all of its range, no portion of its range can be “significant” for purposes of the definitions of “endangered species” and “threatened species.” See the Service's SPR Policy (79 FR 37578, July 1, 2014).

Available Conservation Measures

Conservation measures provided to species listed as endangered or threatened under the Act include recognition, recovery actions, requirements for Federal protection, and prohibitions against certain practices. Recognition through listing results in public awareness and conservation by Federal, State, Tribal, and local agencies; private organizations; and individuals. The Act encourages cooperation with the States and requires that recovery actions be carried out for all listed species. The protection required by Federal agencies and the prohibitions against certain activities are discussed, in part, below.

The primary purpose of the Act is the conservation of endangered and threatened species and the ecosystems upon which they depend. The ultimate goal of such conservation efforts is the recovery of these listed species, so that they no longer need the protective measures of the Act. Subsection 4(f) of the Act requires the Service to develop and implement recovery plans for the conservation of endangered and threatened species. The recovery planning process involves the identification of actions that are necessary to halt or reverse the species' decline by addressing the threats to its survival and recovery. The goal of this process is to restore listed species to a point where they are secure, self-sustaining, and functioning components of their ecosystems.

Recovery planning includes the development of a recovery outline shortly after a species is listed and preparation of a draft and final recovery plan. The recovery outline guides the immediate implementation of urgent recovery actions and describes the process to develop a recovery plan. The plan may be revised to address continuing or new threats to the species, as new substantive information becomes available. The recovery plan identifies recovery criteria for review of when a species may be ready for downlisting (from endangered to threatened) or delisting and methods for monitoring recovery progress. Recovery plans also establish a framework for agencies to coordinate their recovery efforts and provide estimates of the cost of implementing recovery tasks. Recovery teams (composed of species experts, Federal and State agencies, nongovernmental organizations, and stakeholders) are often established to develop recovery plans. If we list Trichomanes punctatum ssp. floridanum, when completed, the draft and final recovery plans would be available on our Web site (http://www.fws.gov/​endangered) or from our South Florida Ecological Services Field Office (see FOR FURTHER INFORMATION CONTACT).

Implementation of recovery actions generally requires the participation of a broad range of partners, including other Federal agencies, States, Tribes, nongovernmental organizations, businesses, and private landowners. Examples of recovery actions include habitat restoration (e.g., restoration of native vegetation), research, captive propagation and reintroduction, and outreach and education. The recovery of many listed species cannot be accomplished solely on Federal lands because their range may occur primarily or solely on non-Federal lands. To achieve recovery of these species requires cooperative conservation efforts on private, State, and Tribal lands.

If this subspecies is listed, funding for recovery actions would be available from a variety of sources, including Federal budgets, State programs, and cost share grants for non-Federal landowners, the academic community, and nongovernmental organizations. In addition, pursuant to section 6 of the Act, the State of Florida would be eligible for Federal funds to implement management actions that promote the protection or recovery of Trichomanes punctatum ssp. floridanum. Information on our grant programs that are available to aid species recovery can be found at: http://www.fws.gov/​grants.

Although Trichomanes punctatum ssp. floridanum is only proposed for listing under the Act at this time, please let us know if you are interested in participating in conservation efforts for this species. Additionally, we invite you to submit any new information on this species whenever it becomes available and any information you may have for conservation planning purposes (see FOR FURTHER INFORMATION CONTACT).

Section 7(a) of the Act requires Federal agencies to evaluate their actions with respect to any species that is proposed or listed as an endangered or threatened species and with respect to its critical habitat, if any is designated. Regulations implementing this interagency cooperation provision of the Act are codified at 50 CFR part 402. Section 7(a)(4) of the Act requires Federal agencies to confer with the Service on any action that is likely to jeopardize the continued existence of a species proposed for listing or result in destruction or adverse modification of proposed critical habitat. If a species is listed subsequently, section 7(a)(2) of the Act requires Federal agencies to ensure that activities they authorize, fund, or carry out are not likely to jeopardize the continued existence of the species or destroy or adversely modify its critical habitat. If a Federal action may affect a listed species or its critical habitat, the responsible Federal agency must enter into consultation with the Service.

Federal agency actions within the subspecies' habitat that may require conference or consultation or both as described in the preceding paragraph include, but are not limited to, federally funded or authorized actions such as habitat restoration and control of nonnatives and any other landscape-altering activities.

With respect to endangered plants, prohibitions outlined at 50 CFR 17.61 make it illegal for any person subject to the jurisdiction of the United States to import or export, transport in interstate or foreign commerce in the course of a commercial activity, sell or offer for sale in interstate or foreign commerce, or to remove and reduce to possession any such plant species from areas under Federal jurisdiction. In addition, for endangered plants, the Act prohibits malicious damage or destruction of any such species on any area under Federal jurisdiction, and the removal, cutting, digging up, or damaging or destroying of any such species on any other area in knowing violation of any State law or regulation, or in the course of any violation of a State criminal trespass law. Exceptions to these prohibitions are outlined in 50 CFR 17.62.

We may issue permits to carry out otherwise prohibited activities involving endangered plants under certain circumstances. Regulations governing permits are codified at 50 CFR 17.62. With regard to endangered plants, the Service may issue a permit authorizing any activity otherwise prohibited by 50 CFR 17.61 for scientific purposes or for enhancing the propagation or survival of endangered plants.

It is our policy, as published in the Federal Register on July 1, 1994 (59 FR 34272), to identify to the maximum extent practicable at the time a species is listed, those activities that would or would not constitute a violation of section 9 of the Act. The intent of this policy is to increase public awareness of the effect of a proposed listing on proposed and ongoing activities within the range of the species proposed for listing. If we list Trichomanes punctatum ssp. floridanum, the following activities could potentially result in a violation of section 9 of the Act; this list is not comprehensive:

(1) Import the subspecies into, or export the subspecies from, the United States without authorization;

(2) Remove and reduce to possession the subspecies from areas under Federal jurisdiction; maliciously damage or destroy the subspecies on any such area; or remove, cut, dig up, or damage or destroy the subspecies on any other area in knowing violation of any law or regulation of any State or in the course of any violation of a State criminal trespass law;

(3) Sell or offer for sale in interstate or foreign commerce the subspecies; except for properly documented antique specimens of the taxon at least 100 years old, as defined by section 10(h)(1) of the Act;

(4) Unauthorized delivering, carrying, or transporting of the subspecies, including import or export across State lines and international boundaries;

(5) Introduction of nonnative species that compete with or prey upon Trichomanes punctatum ssp. floridanum;

(6) Unauthorized release of biological control agents that attack any life stage of this subspecies; and

(7) Unauthorized manipulation or modification of the habitat where Trichomanes punctatum ssp. floridanum is present on Federal lands including, but not limited to, unauthorized water withdrawal from solution holes and unauthorized removal of canopy.

At this time, we are unable to identify specific activities that would not be considered to result in a violation of section 9 of the Act because Trichomanes punctatum ssp. floridanum occurs in a variety of habitat conditions across its range and it is likely that site-specific conservation measures may be needed for activities that may directly or indirectly affect the subspecies.

Questions regarding whether specific activities would constitute a violation of section 9 of the Act should be directed to the South Florida Ecological Services Field Office (see FOR FURTHER INFORMATION CONTACT).

Critical Habitat

Section 3(5)(A) of the Act defines critical habitat as “(i) the specific areas within the geographical area occupied by the species, at the time it is listed . . . on which are found those physical or biological features (I) Essential to the conservation of the species and (II) which may require special management considerations or protection; and (ii) specific areas outside the geographical area occupied by the species at the time it is listed . . . upon a determination by the Secretary that such areas are essential for the conservation of the species.” Section 3(3) of the Act (16 U.S.C. 1532(3)) also defines the terms “conserve,” “conserving,” and “conservation” to mean “to use and the use of all methods and procedures which are necessary to bring any endangered species or threatened species to the point at which the measures provided pursuant to this chapter are no longer necessary.”

Section 4(a)(3) of the Act, as amended, and implementing regulations (50 CFR 424.12), require that, to the maximum extent prudent and determinable, the Secretary shall designate critical habitat at the time the species is determined to be an endangered or threatened species. Our regulations (50 CFR 424.12(a)(1)) state that the designation of critical habitat is not prudent when one or both of the following situations exist:

(1) The species is threatened by taking or other human activity, and identification of critical habitat can be expected to increase the degree of threat to the species, or

(2) such designation of critical habitat would not be beneficial to the species.

As discussed in the Factor B analysis (see above), there is currently no imminent threat of take attributed to collection or vandalism for this species, and identification and mapping of critical habitat is not expected to initiate any such threat. Therefore, in the absence of finding that the designation of critical habitat would increase threats to a species, if there are any benefits to a critical habitat designation, a finding that designation is prudent is warranted. Here, the potential benefits of designation include: (1) Triggering consultation under section 7 of the Act, in new areas for actions in which there may be a Federal nexus where it would not otherwise occur because, for example, it is unoccupied; (2) focusing conservation activities on the most essential features and areas; (3) providing educational benefits to State or county governments or private entities; and (4) preventing people from causing inadvertent harm to the species.

Because we have determined that the designation of critical habitat will not likely increase the degree of threat to the species and may provide some measure of benefit, we determine that designation of critical habitat is prudent for Trichomanes punctatum ssp. floridanum.

Our regulations (50 CFR 424.12(a)(2)) further state that critical habitat is not determinable when one or both of the following situations exists: (1) Information sufficient to perform required analysis of the impacts of the designation is lacking; or (2) the biological needs of the species are not sufficiently well known to permit identification of an area as critical habitat.

Our regulations at 50 CFR 424.19 require the Service to “make available for public comment the draft economic analysis of the designation” at the time the proposed critical habitat rule is published in the Federal Register. At this point, a careful assessment of the economic impacts that may occur due to a critical habitat designation is still ongoing, and we are still in the process of acquiring the information needed to perform this assessment. Accordingly, we find designation of critical habitat for Trichomanes punctatum ssp. floridanum to be not determinable at this time.

Required Determinations

Clarity of the Rule

We are required by Executive Orders 12866 and 12988 and by the Presidential Memorandum of June 1, 1998, to write all rules in plain language. This means that each rule we publish must:

(1) Be logically organized;

(2) Use the active voice to address readers directly;

(3) Use clear language rather than jargon;

(4) Be divided into short sections and sentences; and

(5) Use lists and tables wherever possible.

If you feel that we have not met these requirements, send us comments by one of the methods listed in the ADDRESSES section. To better help us revise the rule, your comments should be as specific as possible. For example, you should tell us the numbers of the sections or paragraphs that are unclearly written, which sections or sentences are too long, the sections where you feel lists or tables would be useful, etc.

National Environmental Policy Act

We have determined that environmental assessments and environmental impact statements, as defined under the authority of the National Environmental Policy Act need not be prepared in connection with listing a species as an endangered or threatened species under the Act. We published a notice outlining our reasons for this determination in the Federal Register on October 25, 1983 (48 FR 49244).

Government-to-Government Relationship With Tribes

In accordance with the President's memorandum of April 29, 1994 (Government-to-Government Relations with Native American Tribal Governments; 59 FR 22951), Executive Order 13175 (Consultation and Coordination with Indian Tribal Governments), and the Department of the Interior's manual at 512 DM 2, we readily acknowledge our responsibility to communicate meaningfully with recognized Federal tribes on a government-to-government basis. In accordance with Secretarial Order 3206 of June 5, 1997 (American Indian Tribal Rights, Federal-Tribal Trust Responsibilities, and the Endangered Species Act), we readily acknowledge our responsibilities to work directly with tribes in developing programs for healthy ecosystems, to acknowledge that tribal lands are not subject to the same controls as Federal public lands, to remain sensitive to Indian culture, and to make information available to tribes. We are not aware of any Trichomanes punctatum ssp. floridanum populations on tribal lands.

References Cited

A complete list of references cited in this rulemaking is available on the Internet at http://www.regulations.gov and upon request from the South Florida Ecological Services Field Office (see FOR FURTHER INFORMATION CONTACT).

Authors

The primary authors of this proposed rule are the staff members of the South Florida Ecological Services Field Office.

List of Subjects in 50 CFR Part 17

• Endangered and threatened species
• Exports
• Imports
• Reporting and recordkeeping requirements
• Transportation

Proposed Regulation Promulgation

Accordingly, we propose to amend part 17, subchapter B of chapter I, title 50 of the Code of Federal Regulations, as set forth below:

PART 17—[AMENDED]

1. The authority citation for part 17 continues to read as follows:

Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C. 4201-4245, unless otherwise noted.

2. Amend § 17.12(h) by adding an entry for “ Trichomanes punctatum ssp. floridanum” to the List of Endangered and Threatened Plants in alphabetical order under FERNS AND ALLIES to read as follows:

§ 17.12

Endangered and threatened plants.

* * * * *

(h) * * *

Species		Historic range	Family	Status	When listed	Critical habitat	Special rules
Scientific name	Common name
*         *         *         *         *         *         *
FERNS AND ALLIES
*         *         *         *         *         *         *
Trichomanes punctatum ssp. floridanum	Florida bristle fern	U.S.A. (FL)	Hymenophyllaceae	E		NA	NA.
*         *         *         *         *         *         *

* * * * *

Dated: September 26, 2014.

Rowan W. Gould,

Acting Director, U.S. Fish and Wildlife Service.